Materials Handbook 15th ed - G. Brady_ H. Clauser_ J. Vaccari (McGraw-Hill_ 2002) Episode 13 pptx

Because of titanium’s highly reactive nature in the presence ofsuch gases as oxygen, the casting must be done in a vacuum furnace.Because of their high strength-to-weight ratio primarily

LT-125 is a water-soluble organo-trialkyl-tin used as a bacteriocide

in paper and textile processing It can be used over a wide pH range

TINPLATE. Soft-steel plate containing a thin coating of pure tin onboth sides A large proportion of the tinplate used goes into the manu-facture of food containers because of its resistance to the action ofvegetable acids and its nonpoisonous character It solders easily, andalso is easier to work in dies than terneplate, so that it is preferredover terneplate for making toys and other cheap articles in spite of ahigher cost Commercial tinplate comes in boxes of 112 sheets, 14 by

20 in (0.36 by 0.51 m), and is designated by the net weight per boxwhen below 100 lb (45 kg) Heavy tinplate above 100 lb (45 kg) goes

by number, as steel does, or by letter symbols The weight of tin may

be as high as 1.7% of the total weight of the sheet Coke plates carry

as little tin as is necessary to protect and brighten the plate for porary use The tin of the coat forms compounds of FeSn2, Fe2Sn, andFeSn with the iron of the plate, and on a coke plate this compound is0.00006 to 0.00015 in (0.00015 to 0.00038 cm) thick Best cokes carry

tem-more tin than do the standard cokes Charcoal plates have heavier

coats of tin designated by the letter A The AAAAAA, or 6A, has theheaviest coating Tinplate is made by the hot-dip process using palmoil as a flux, or by a continuous electroplating process A base box con-tains 31,360 in2(20 m2) of tinplate, and standard-dip tinplate has 1.5

lb (0.7 kg) of tin per base box, while electrolytic plate has only 0.25 lb

(0.1 kg) of tin per base box and much electrolytic tinplate for

con-tainer use has only 0.10 lb (0.05 kg) of tin per base box.Electrotinning gives intimately adherent coatings of any desiredthickness, and the plate may have a serviceable coat as thin as0.00003 in (0.00008 cm), or about one-third that of the thinnest possi-ble dipped plate A slight cold rolling of electrolytic tinplate gives abright, smooth finish

Taggers was originally a name for tinplate that is undersized, or

below the gage of the plate in the package, but the name taggers tin

is also applied to light-gage plate These sizes are No 38 gage, 55 lb

(25 kg); No 37, 60 lb (27 kg); and No 36, 65 lb (29 kg) Ductilite, of

Wheeling-Pittsburgh Steel Corp., is a tinplate that is not made by hotrolling in packs, but is cold-rolled from single hot-rolled strip steel It

is of uniform gage and does not have the thin edges of pack-rolled

plate It also has a uniform grain structure Weirite, of Weirton Steel Corp., is cold-reduced coke tinplate Black plate, used for cans in

place of tinplate where the tin protection is not necessary, is notblack, but is any sheet steel other than tinplate or terneplate in tin-plate sizes It may be chemically treated to resist rust or corrosion

Electroplated tin-zinc coatings, developed at the International

Tin Research Institute (ITRI) in England in the late 1940s, are morecorrosion-protective of steel than zinc alone However, bath control isdifficult, and the sodium stannate and cyanide systems of the originalbath are toxic In the early 1990s, ITRI developed the Stanzecprocess, which is cyanide-free, nontoxic, and more controllable Theelectrolyte, or bath, is a mixture of sodium or potassium stannate,sodium or potassium zincate, sodium or potassium hydroxide, pluscomplexing and stabilizing agents, brighteners, and grain refiners.Any alloy composition can be deposited by barrel, brush, or rack plat-ing, and deposits of 70 to 80% tin with the balance zinc combine sol-derability with good corrosion resistance A 75Sn–25Zn plate has aVickers hardness of 37, and the coatings are typically ductile andsuitable for painting They also can be plated to brasses and high-copper alloys and are considered alternatives to plating withtoxic cadmium in many applications

TITANATES. Compounds made by heating a mixture of an oxide orcarbonate of a metal and titanium dioxide High dielectric constants,high refractive indices, and ferroelectric properties contribute primar-

ily to their commercial importance Barium titanate crystals,

BaTiO3, are made by die-pressing titanium dioxide and barium bonate and sintering at high temperature This crystal belongs to the

car-class of perovskite in which the closely packed lattice of barium and

oxygen ions has a barium ion in each corner and an oxygen ion in thecenter of each face of a cube with the titanium ion in the center of theoxygen octahedron Because of their high dielectric constant and com-patibility with high-temperature superconductors, thin perovskiteoxide films are candidates for tunable microwave devices For piezo-electric use the crystals are subjected to a high current, and they give

a quick response to changes in pressure or electric current They also

store electric charges and are used for capacitors Glennite 103, of Gulton Industries Inc., is a piezoelectric ceramic molded from bar- ium titanate modified with temperature stabilizers Bismuth stan-

nate, Bi2(SnO3) 5H2O, a crystalline powder that dehydrates at about284°F (140°C), may be used with barium titanate in capacitors to

increase stability at high temperatures Ceramelex is molded crystalline barium titanate Lead zirconate–lead titanate is a

poly-piezoelectric ceramic that can be used at higher temperatures than

barium titanate Lead titanate, PbTiO3, is used as a less costly stitute for titanium oxide It is yellowish and has only 60% of the hid-

sub-ing power, but is very durable and protects steel from rust Butyl

titanate is a yellow, viscous liquid used in anticorrosion varnishes

and for flameproofing fabrics It is a condensation product of thetetrabutyl ester of ortho-titanic acid, and contains about 36% tita-

nium dioxide Calcium titanate, CaTiO3, occurs in nature as themineral perovskite As a ceramic, it has a room-temperature dielectricconstant of about 160 It is frequently used as an addition to bariumtitanate or by itself as a temperature-compensating capacitor

Magnesium titanate, MgTiO3, crystallizes as an ilmenite ratherthan a perovskite structure It is not ferroelectric, and is used withtitanium dioxide to form temperature-compensating capacitors It has

also been used as an addition agent to barium titanate Strontium

titanate, SrTiO3, has a cubic perovskite structure at room ture It has a dielectric constant of about 230 as a ceramic, and it iscommonly used as an additive to barium titanate to decrease theCurie temperature By itself, it is used as temperature-compensatingmaterial because of its negative temperature characteristics

tempera-Strontium titanate, used as a brilliant diamondlike gemstone, is a

strontium mesotrititanate Stones are made up to 4 carats Therefractive index is 2.412 It has a cubic crystal similar to the diamond,

but the crystal is opaque in the X-ray spectrum Crystalline

silico-titanate, developed at Texas A&M University and Sandia National

Laboratories, has potential use in the cleanup of radioactive wastes

As an inorganic ion-exchange agent, it promotes exchange of residentsodium ions for ions of radioactive elements It has proved effective inremoving cesium from neutral and highly acidic waste solutions

Titanate fibers can be used as reinforcement in thermoplastic

mold-ings The fibers, called Fybex, produced by LNP Engineering

Plastics, Inc., can also be used in plated plastics to reduce thermalexpansion, warpage, and shrinkage Titanate fibers in plastics alsoprovide opacity

TITANIUM AND TITANIUM ALLOYS. A metallic element, symbol Ti,occurring in a great variety of minerals It was first discovered as anelement in 1791 in a black magnetic sand at Manachin, Cornwall,

England, and called menachite, from the name of the sand,

mena-chinite Its chief commercial ores are rutile and ilmenite In rutile it

occurs as an oxide It is an abundant element but is difficult to reduce

from the oxide High-purity titanium (99.9%) has a melting point of

about 3034°F (1668°C), a density of 0.163 lb/in3 (4,512 kg/m3), andtensile properties at room temperature of about 34,000 lb/in2 (234MPa) ultimate strength, 20,000 lb/in2 (138 MPa) yield strength, and54% elongation It is paramagnetic and has low electrical conductivityand thermal expansion

The commercial metal is produced from sponge titanium, which is

made by converting the oxide to titanium tetrachloride followed by

962 TITANIUM AND TITANIUM ALLOYS

reduction with molten magnesium The metal can also be produced indendritic crystals of 99.6% purity by electrolytic deposition from tita-nium carbide Despite its high melting point, titanium reacts readily

in copper and in other metals and is much used for alloying and fordeoxidizing It is a more powerful deoxidizer of steel than silicon or

manganese An early German deoxidizing alloy known as Badin

metal contained about 9% aluminum, 19 silicon, 5 titanium, and the

balance iron Titanium copper, used for deoxidizing nonferrous

met-als, is made by adding titanium to molten copper The congealed alloy

is broken into lumps

One of the chief uses of the metal has been in the form of titaniumoxide as a white pigment It is also valued as titanium carbide forhard facings and for cutting tools Small percentages of titanium areadded to steels and alloys to increase hardness and strength by theformation of carbides or oxides or, when nickel is present, by the for-

mation of nickel titanide The first titanium alloys in the United

States were produced in 1945 by the Bureau of Mines

Titanium is one of the few allotropic metals (steel is another); that

is, it can exist in two different crystallographic forms At room perature, it has a close-packed hexagonal structure, designated as the

tem-alpha phase At around 1625°F (884°C), the tem-alpha phase transforms

to a body-centered cubic structure, known as the beta phase, which is

stable up to titanium’s melting point of about 3050°F (1677°C).Alloying elements promote formation of one or the other of the twophases Aluminum, for example, stabilizes the alpha phase; that is, itraises the alpha to the beta transformation temperature Other alphastabilizers are carbon, oxygen, and nitrogen Beta stabilizers, such ascopper, chromium, iron, molybdenum, and vanadium, lower the trans-formation temperature, therefore allowing the beta phase to remainstable at lower temperatures, and even at room temperature.Titanium’s mechanical properties are closely related to theseallotropic phases For example, the beta phase is much stronger, butmore brittle, than the alpha phase Titanium alloys therefore can beusefully classified into three groups on the basis of allotropic phases:alpha, beta, and alpha-beta alloys

Titanium and its alloys have attractive engineering properties.They are about 40% lighter than steel and their moderate weight andhigh strengths, up to 200,000 lb/in2(1,379 MPa), gives titanium alloysthe highest strength-to-weight ratios of any structural metal.Furthermore, this exceptional strength-to-weight ratio is maintainedfrom 420°F (216°C) up to 1000°F (538°C) A second outstandingproperty of titanium materials is their corrosion resistance The pres-ence of a thin, tough, oxide surface film provides excellent resistance

to atmospheric and sea environments as well as a wide range of

TITANIUM AND TITANIUM ALLOYS 963

chemicals, including chlorine and organics containing chlorides.Being near the cathodic end of the galvanic series, titanium performsthe function of a noble metal Titanium and its alloys, however, canreact pyrophorically in certain media Explosive reactions can occurwith fuming nitric acid containing less than 2% water or more than 6nitrogen dioxide and, on impact, with liquid oxygen Pyrophoric reac-tions also can occur in anhydrous liquid or gaseous chlorine, liquidbromine, hot gaseous fluorine, and oxygen-enriched atmospheres.Fabrication is relatively difficult because of titanium’s susceptibil-ity to hydrogen, oxygen, and nitrogen impurities, which cause embrit-tlement Therefore elevated-temperature processing, includingwelding, must be performed under special conditions that avoid diffu-sion of gases into the metal Heat is usually required in most formingoperations.

Commercially pure titanium and many of the titanium alloys arenow available in most common wrought mill forms, such as plate,sheet, tubing, wire, extrusions, and forgings Castings can also beproduced in titanium and some of the alloys, investment casting andgraphite-mold (rammed graphite) casting being the principal meth-ods Because of titanium’s highly reactive nature in the presence ofsuch gases as oxygen, the casting must be done in a vacuum furnace.Because of their high strength-to-weight ratio primarily, titanium andtitanium alloys are widely used for aircraft structures requiringgreater heat resistance than aluminum alloys Because of their excep-tional corrosion resistance, however, they (unalloyed titanium pri-marily) are also used for chemical processing, desalination, and powergeneration equipment; marine hardware; valve and pump parts; andprosthetic devices

There are several grades of commercially pure titanium, also called unalloyed titanium They are distinguished by their impu-

rity content, that is, the maximum amount of carbon, nitrogen, gen, iron, and oxygen permitted Regardless of grade, carbon andhydrogen contents are 0.10 and 0.015% maximum, respectively.Maximum nitrogen is 0.03%, except for 0.05 in Grades 3 and 4 Ironcontent ranges from as much as 0.20% in Grade 1, the most pure(99.5) grade, to as much as 0.05 in Grade 4, the least pure (98.9).Maximum oxygen ranges from 0.18% in Grade 1 to 0.40 in Grade 4.Grade 7, 99.1% pure based on maximum impurity content, is actually

hydro-a series of hydro-alloys conthydro-aining 0.12 to 0.25% phydro-allhydro-adium for improved rosion resistance in hydrochloric, phosphoric, and sulfuric acid solu-tions Palladium content has little effect on tensile properties, butimpurity content, especially oxygen and iron, has an appreciableeffect Minimum tensile yield strengths range from 25,000 lb/in2(172

cor-964 TITANIUM AND TITANIUM ALLOYS

MPa) for Grade 1 to 70,000 lb/in2 (483 MPa) for Grade 4 Grade 16,from Oremet–Wah Chang, has only 0.05% palladium and, thus is less

costly than Grade 7 alloys Titanium-ruthenium alloy Ti-0.2Ru,

developed by the research group Mintek of South Africa, is said tomatch the corrosion resistance of Grade 7 alloys at lower cost Its ulti-mate tensile strength is 84,000 lb/in2(579 MPa) and the elongation isabout 23%, both greater than those of Grade 7

There are three principal types of titanium alloys: alpha or near-alpha alloys, alpha-beta alloys, and beta alloys All are avail-able in wrought form and some of each type for castings as well Inrecent years, some also have become available in powder composi-tions for processing by hot isostatic pressing and other powder-met-

allurgy techniques Titanium alpha alloys typically contain

aluminum and usually tin Other alloying elements may include conium, molybdenum, and, less commonly, nitrogen, vanadium,columbium, tantalum, or silicon Though they are generally not capa-ble of being strengthened by heat treatment (some will respondslightly), they are more creep-resistant at elevated temperature thanthe other two types, are preferred for cryogenic applications, and are

zir-more weldable but less forgeable Ti-5Al-2Sn, which is available in regular and ELI grades (extra-low interstitial) in wrought and cast

forms, is the most widely used In wrought and cast form, minimumtensile yield strengths range from 90,000 lb/in2(621 MPa) to 115,000lb/in2(793 MPa) and tensile modulus is on the order of 15.5  106 to

16  106 lb/in2 (106,873 to 110,320 MPa) It has useful strength toabout 900°F (482°C) and is used for aircraft parts and chemical pro-cessing equipment The ELI grade is noted for its superior toughnessand is preferred for containment of liquid gases at cryogenic temper-atures Other alpha or near-alpha alloys and their performance bene-

fits include Ti-8Al-1Mo-1V (high creep strength to 900°F),

Ti-6Al-2Sn-4Zr-2Mo [creep resistance and stress stability to 1100°F

(593°C)], Ti-6Al-2Cb-1Ta-0.8Mo (toughness, strength, weldability), and Ti-2.25Al-11Sn-5Zr-1Mo [high tensile strength—135,000 lb/in2

(931 MPa) yield, superior resistance to stress corrosion in hot salt

media at 900°F] Another alpha alloy, Ti-0.3Mo-0.8Ni, also known as

TiCode 12, is noted for its greater strength than commercially pure

grades and equivalent or superior corrosion resistance, especially to

crevice corrosion in hot salt solutions The near alpha alloy

Ti-5Al-1Sn-1Zr-1V-0.8Mo combines good toughness and weldability, corrosion

and stress-corrosion resistance, and room-temperature creep resistance.Developed by Titanium Metals Corp., it has longitudinal tensile yieldstrength of 103,000 to 116,000 lb/in2(710 to 800 MPa), depending onsheet and plate thickness, and elongation of 10 to 15% Machinability

TITANIUM AND TITANIUM ALLOYS 965

and forgeability are quite similar to those of the alpha-beta Ti-6Al-4Valloy The alloy is said to be ideal for marine fasteners.

Titanium alpha-beta alloys, which can be strengthened by

solu-tion heat treatment and aging, afford the opportunity of parts tion in the more ductile annealed condition and then can be

fabrica-heat-treated for maximum strength Ti-6Al-4V, which is available in

regular and ELI grades, is the principal alloy, its production alonehaving accounted for about half of all titanium and titanium-alloyproduction In the annealed condition, tensile yield strength is about130,000 lb/in2 (896 MPa) and 13% elongation Solution treating andaging increase yield strength to about 150,000 lb/in2 (1,034 MPa).Yield strength decreases steadily with increasing temperature, toabout 70,000 lb/in2 (483 MPa) at about 950°F (510°C) for the agedalloy At 850°F (454°C), aged bar has a 1,000-h stress-rupturestrength of about 50,000 lb/in2 (345 MPa) Uses range from aircraftand aircraft turbine parts to chemical processing equipment, marinehardware, and prosthetic devices The alloy is also the principal alloyused for superplastically formed, and superplastically formed andsimultaneously diffusion-bonded, parts At 1650 to 1700°F (899 to927°C) and low strain rates, the alloy exhibits tensile elongations of

600 to 1,000%, a temperature range also amenable to

diffusion-bond-ing the alloy SP700, from Japan’s NKK Corp., exhibits some 2,000%

elongation at about 1420°F (770°C)

Although Ti-6Al-4V and Ti-6Al-4V ELI have served for armor

plate—the latter being superior—less expensive titanium armor

alloys have been introduced by Oremet–Wah Chang They contain

2.5 to 5.4% aluminum, 2.0 to 3.4 vanadium, 0.2 to 2 iron, and 0.2 to0.3 oxygen

Following are other alpha-beta alloys and their noteworthy

charac-teristics Ti-6Al-6V-2Sn: high strength to about 600°F (315°C) but low toughness and fatigue resistance Ti-8Mn: limited use for flat mill products, not weldable Ti-7Al-4Mo: a forging alloy mainly, but

limited use; and a 150,000 lb/in2 (1,034 MPa) yield strength in the

aged condition Ti-6Al-2Sn-4Zr-6Mo: high strength, 170,000 lb/in2

(1,172 MPa) yield strength, decreasing to about 110,000 lb/in2 (758MPa) at 800°F (427°C); for structural applications at 750 to 1000°F

(400 to 540°C) Ti-5Al-2Sn-2Zr-4Mo-4Cr and

Ti-6Al-2Sn-2Zr-2Mo-2Cr: superior hardenability for thick-section forgings; high

modu-lus—about 17  106 to 18  106 lb/in2 (117,215 to 124,110 MPa),respectively; tensile yield strength of about 165,000 lb/in2 (1,138MPa) Ti-6Al-2Sn-2Zr-2Mo-2Cr castings of the same nominal composi-tion as the wrought alloy except for a reduction of silicon to 0.1% byweight also exhibit good mechanical performance after hot isostatic

966 TITANIUM AND TITANIUM ALLOYS

pressing Tensile properties for several duplex and triplex heat ments, and thicknesses of 0.5 to 1.5 in (12.5 to 37.5 mm), demonstrateultimate strengths of 142,000 to 154,000 lb/in2 (979 to 1,062 MPa),yield strengths of 127,000 to 135,000 lb/in2 (876 to 931 MPa), elonga-tions of 6.7 to 11.9%, and average fracture toughness of 97,800 to125,000 lb/in2 in0.5 (108 to 140 MPa m0.5) Ti-10V-2Fe-3Al: best of

treat-the alloys in toughness at a yield strength of 130,000 lb/in2 (896MPa); can also be aged to a yield strength of about 172,000 lb/in2

(1,186 MPa); intended for use at temperatures to about 600°F

(315°C) Ti-3Al-2.5V: a tubing and fastener alloy primarily, moderate

strength and ductility, weldable

Beta titanium alloys, fewest in number, are noted for their

hard-enability, good cold formability in the solution-treated condition, andhigh strength after aging On the other hand, they are heavier thantitanium and the other alloy types, their density ranging from about0.174 to 0.175 lb/in3(4.84 g/cm3) for Ti-13V-11Cr-3Al, Ti-8Mo-8V-2Fe-

3Al, and Ti-3Al-8V-6Cr-4Zr-4Mo to 0.183 lb/in3 (5,065 kg/m3) for

Ti-11.5Mo-6Zr-4.5Sn, which is also known as Beta III They are also the

least creep-resistant of the alloys Ti-13V-11Cr-3Al, a weldable alloy,can be aged to tensile yield strengths as high as 195,000 lb/in2 (1,345MPa) and retains considerable strength at temperatures to 600°F, buthas limited stability at prolonged exposure to higher temperatures

Timetal 21S, of Titanium Metals Corp., is a metastable beta alloy

of composition Ti-15Mo-3Al-2.7Cb-0.3Fe-0.2Si-0.13O with

maxi-mum amounts of 0.05% carbon, 0.05 nitrogen, 0.015 hydrogen, and0.4 residual elements It is unique among titanium and titaniumalloys in its resistance to Skydrol, a widely used aircraft hydraulicfluid Also, its oxidation resistance at 1200°F (649°C) is far superior tothat of commercially pure titanium Aging at 1000°F (538°C) results

in tensile yield strengths of 179,000 to 187,000 lb/in2 (1,234 to 1,289MPa) The alloy can be rolled to thin foil, a form useful for metal-

matrix composites Timetal 15-3, of the nominal composition

Ti-15V-3Al-3Cr-3Sn, is another metastable beta alloy It is a high-strength,

cold-formed strip alloy with ultimate tensile strength of 145,000 to180,000 lb/in2 (1,000 to 1,241 MPa), tensile yield strengths of 140,000

to 170,000 lb/in2 (965 to 1,172 MPa) and elongations of 5 to 7%,depending on aging temperature and time after solution heat-treat-ment and air cooling

Timetal LCB (low-cost beta), a Ti-6.8Mo-4.5Fe-1.5Al alloy of the

same company, reduces formulating cost because iron need not beremoved from the ore It is a candidate for replacing steel spring wireand requires processing temperatures of only 300 to 400°F (149 to204°C) The alloy has a tensile strength of 150,000 lb/in2(1,034 MPa)

TITANIUM AND TITANIUM ALLOYS 967

and a tensile modulus of 16.5  106 lb/in2 (113,768 MPa).

Oremet–Wah Chang’s Tiadyne 3515, also known as Titanium Alloy

C and Ti-1270, contains 50% titanium, 35 vanadium, and 15

chromium It is noted for high-temperature strength and the ability

to resist combustion in air at temperatures and pressures far greaterthan for Ti-6Al-4V alloy The average tensile yield strength is 137,000lb/in2 (945 MPa), 98,000 lb/in2 (676 MPa) at 1000°F (538°C) It isavailable in rod, various flat products, and powder, and is also

castable Tiadyne 3510 contains about 35% zirconium, 10.5

columbium, and 0.07 to 0.13 oxygen Though rather heavy (density is0.19 lb/in3, 5,300 kg/m3) and having a low modulus (10.4  106lb/in2,71,700 MPa), tensile yield strength is 160,000 lb/in2 (1,103 MPa),weldability is good and the alloy can be surface hardened by oxidationfor high wear resistance It is also superplastic at certain elevatedtemperatures and is at least as corrosion resistant as commerciallypure titanium Prosthetic devices, firearm firing mechanisms, and

springs are potential uses Ti-45Cb, of this company, features

supe-rior resistance to oxidizing environments and combustion in pureoxygen The alloy has a density of 0.206 lb/in3(5,702 kg/m3), an ulti-mate tensile strength of 80,000 lb/in2 (552 MPa), a tensile yieldstrength of 70,000 lb/in2 (483 MPa)—29,000 lb/in2 (200 MPa) at752°F (400°C)—23% elongation, and a modulus of elasticity of 9 

106 lb/in2(62,055 MPa) Its corrosion resistance may be slightly ter than that of titanium in sulfuric acid and in hydrochloric acid atconcentrations of less than 20% Ti-45Cb has been used for auto-clave vent lines in processing gold ores, for parts of oxygen injectorsexposed to pure oxygen, and, for hot wet-oxidation equipment used

bet-in wastewater processbet-ing Applications bet-include aerospace rivets,high-pressure oxygenated gas vents, oxygen lances for pressure oxi-dation reactors, valves for corrosive oxygenated processes, andsuperconducting wire

In an effort to spur nonaerospace uses, manufacturers have duced several low-cost titanium alloys which are roughly similar instrength to aerospace alloy Ti-6Al-4V but which may sacrifice certainperformance features required in aerospace applications These alloys

intro-include titanium alloy Auto-grade, of Allvac, titanium alloys RM and VM of RMI Titanium Co., and Timetal-62S of Titanium Metals

Corp To reduce cost, Auto-grade is initially forged and rolled in thebeta region, then rolled in the alpha-beta range RM, made of recycledmaterial, has a nominal Ti-6Al-4V composition VM, for virgin metal,

is Ti-6.4Al-1.2Fe, the iron substituting for more-costly vanadium.

Timetal-62S, Ti-6Al-1.7Fe-0.1Si, also uses iron instead of vanadiumand costs about 25% less than the aerospace alloy

968 TITANIUM AND TITANIUM ALLOYS

Titanium alloys are leading candidates for metal-matrix ites, primarily for aircraft and aircraft engine applications Siliconcarbide fiber is a leading reinforcement One approach, developed by

compos-Howmet Corp and General Electric Aircraft Engines, is called ing Preforms of alloys reinforced with the fiber are cast within a

bicast-matrix alloy

TITANIUM CARBIDE. A hard, crystalline powder of composition TiCmade by reacting titanium dioxide and carbon black at temperaturesabove 3272°F (1800°C) It is compacted with cobalt or nickel for use incutting tools and for heat-resistant parts It is lighter in weight andless costly than tungsten carbide, but in cutting tools it is more brit-tle When combined with tungsten carbide in sintered carbide toolmaterials, however, it reduces the tendency to cratering in the tool Ageneral-purpose cutting tool of this type contains about 82% tungsten

carbide, 8 titanium carbide, and 10 cobalt binder Kentanium, of

Kennametal, Inc., is titanium carbide in various grades with up to40% either cobalt or nickel as the binder, used for high-temperature,erosion-resistant parts For highest oxidation resistance, only about

5% cobalt binder is used Kentanium 138, with 20% cobalt, is used

for parts where higher strength and shock resistance are needed, andwhere temperatures are below about 1800°F (982°C) This materialhas a tensile strength of 45,000 lb/in2 (310 MPa), compressivestrength of 550,000 lb/in2 (3,792 MPa), and Rockwell A hardness 90

Kentanium 151A, for resistance to molten glass or aluminum, has a

binder of 20% nickel Titanium-carbide alloy, of Ford Motor Co., for

tool bits, has 80% titanium carbide dispersed in a binder of 10 nickeland 10 molybdenum The material has a Rockwell A hardness of 93

and a dense, fine-grained structure Ferro-Tic, of Chromalloy Corp.,

has titanium carbide bonded with stainless steel It has a Rockwell C

hardness of 55 Machinable carbide is titanium carbide in a matrix

of Ferro-Tic C tool steel Titanium carbide tubing is produced in

round or rectangular form 0.10 to 3 in (0.25 to 7.6 cm) in diameter, byTEEG Research, Inc It is made by vapor deposition of the carbidewithout a binder The tubing has a Knoop hardness above 2,000 and amelting point of 5880°F (3249°C) Grown single crystals of titaniumcarbide of Linde Co have composition TiC0.94, with 19% carbon Themelting point is 5882°F (3250°C), specific gravity 4.93, and Vickershardness 3,230

TITANIUM ORES. The most common titanium ores are ilmenite andrutile Ilmenite is an iron-black mineral having a specific gravity of

about 4.5 and containing about 52% titanic oxide, or titania, TiO2

The ore of India is sold on the basis of titanium dioxide content, andthe high-grade ore averages about 60% TiO2, 22.5 iron, and 0.4 silica.

Ilmenite is a ferrotitanate, FeO TiO2, but much of the material

called ilmenite is arizonite, Fe2O3 3TiO2 Titanium ores are widelydistributed and plentiful Ilmenite is found in northern New York,Florida, North Carolina, and in Arkansas, but the most extensive,accessible resources are found in Canada The Quebec ilmenite con-tains 30% iron The concentrated ore has about 36% TiO2, and 41iron, and is smelted to produce pig iron and a slag containing 70 TiO2which is used to produce titanium oxide The beach sands of Senegalare mixed ores, the ilmenite containing 55 to 58% TiO2, and the zir-

coniferous quartz containing 70 to 90 zirconia The beach sands of

Brazil are washed to yield a product averaging 71.6% ilmenite, 13 con, and 6 monazite The Indian ilmenite also comes from beachsands The ore of New York State averages 19% TiO2

zir-Rutile is a titanium dioxide, TiO2, containing theoretically 60%titanium Its usual occurrence is crystalline or compact massive, with

a specific gravity of 4.18 and 4.25 and Mohs hardness 6 to 6.5 Thecolor is red to brown, occasionally black Rutile is found in granite,gneiss, limestone, or dolomite It is obtained from beach sand ofnorthern Florida and Espirito Santo, Brazil, and is also produced in

Virginia, and in Australia and India Rutile and brookite and

Octahedrite, or anatase, are produced in Arkansas and

Massachusetts The best Virginia concentrates are 92.5 to 98% TiO2,but some are 42% from rock originally showing 18.5 TiO2 in a body offeldspar Rutile is marketed in the form of concentrates on the basis

of 79 to 98.5% titanium oxide It is used as an opacifier in ceramicglazes and to produce tan-colored glass It is also employed for weld-ing-rod coatings On welding rods it aids stabilization of the arc and

frees the metal of slag Tanarc, used on welding rods as a

replace-ment for rutile, is made from slag from Canadian titaniferoushematite, and it contains 70% TiO2

TITANIUM OXIDE The white titanium dioxide, or titania, of

compo-sition TiO2, is an important paint pigment The best quality is duced from ilmenite, and is higher in price than many whitepigments but has great hiding power and durability Off-color pig-ments, with a light buff tone, are made by grinding rutile ore Thepigments have fine physical qualities and may be used wherever thecolor is not important In the mid-1980s, TiO2production moved fromthe sulfate process to the chloride process for environmental concernsand better performance The rutile feedstocks of the latter process areless photocatalytically active than the former anatose feedstocks; they

have a slightly higher refractive index, thus better ability to scatterlight; and they accept more readily and bond more strongly to variouscoatings used to aid dispersion in processing Titania is also substi-

tuted for zinc oxide and lithopone in the manufacture of white

rub-ber goods, and for paper filler The specific gravity is about 4 Mixed

with blanc fixe, it is also marketed under the name of Titanox.

Zopaque is a pure titanium oxide for rubber compounding Ti-Pure

of Du Pont is commercially pure titanium dioxide for pigment use

Duolith, of this company, is titanated lithopone pigment containing

15% titanium dioxide, 25 zinc sulfide, and 60 barium sulfate

Titanium dioxide is also widely used as a photocatalyst In anatose

form, it is the most commonly used catalyst in solar photocatalyticdetoxifications for, say, destroying bacteria A titanium dioxide photo-catalytic film, developed by Toto Ltd of Japan, has silver and coppercompounds immobilized on the surface to kill bacteria when exposed

to fluorescent light It is used to coat ceramic tiles in hospitals, foodand chemical processing plants, and other sanitary applications

Titania crystals are produced in the form of pale-yellow,

single-crystal boules for making optical prisms and lenses for applicationswhere the high refractive index is needed The crystals are also used

as electric semiconductors, and for gemstones They have a higherrefractive index than the diamond, and the cut stones are more bril-liant but are much softer Knoop hardness is about 925, and the melt-ing point is 3317°F (1825°C) The refractive index of the rutile form is2.7, and that of the anatase is 2.5, while the synthetic crystals have a

refractive index of 2.616 vertically and 2.903 horizontally Tiona

RCL-188, from SCM Chemicals, is 50 to 80% titanium dioxide in a

polyethylene carrier It is intended to improve the melt flow rate ofvarious plastics

Titanium oxide is a good refractory and electrical insulator Thefinely ground material gives good plasticity without binders and is

molded to make resistors for electronic use Micro sheet is titanium

oxide in sheets as thin as 0.003 in (0.008 cm) for use as a substitutefor mica for electrical insulation where brittleness is not important

Titania-magnesia ceramics were made in Germany in the form of

extruded rods and plates and pressed parts

TOBACCO. The leaf of an unbranched annual plant of the genus

Nicotiana, of which there are about 50 species and many varieties It

is used for smoking, chewing, snuff, insecticides, and production ofthe alkaloid nicotine Commercial crops are grown in about 60 coun-tries, but about one-third of world production is in the United States

Only two species are grown commercially, N tabacum, a tropical

plant native to the West Indies and South America, and N rustica,

grown by the Indians of Mexico and North America before 1492

About 85% of world production is now from N tabacum, and there are

more than 100 varieties of this plant

Tobacco was not known in Europe until it was brought from theWest Indies by Columbus Plants for cultivation were brought to Spain

in 1558, and by 1586 smoking had become a general practice in ern Europe The first commercial shipments were made from Virginia

west-in 1618, the growwest-ing of cultured varieties havwest-ing begun west-in 1612.Smoking of tobacco was practiced by the Indians from Canada toPatagonia, and the natives of Haiti used powdered tobacco leaf as

snuff under the name of cohoba Like Indian corn, the tobacco plant

had been domesticated for centuries, and the original wild ancestor ofthe plant is not known Some Indian tribes, such as the Tobacco nation

of southwest Ontario, specialized in the growing of tobacco types

The quality of the tobacco leaf varies greatly with the soil and mate, the care of the plant, and the curing of the leaf; the nicotine con-tent develops in the curing process The narcotic effects are due to the

cli-alkaloid nicotine, C10H14N2, a complex pyrrolidine, which is a heavy,water-white oil The nicotine is absorbed through the mucous mem-branes of the nose and throat The aroma and flavor come from theessential oils in the leaf developed during fermentation and curing The more harmful effects to the eyes and respiratory system come from

the pyridine C5H5N, a toxic aromatic compound that also occurs incoal tar, and from other elements of the smoke and not from the alka-

loid The burning of the tars may also produce carcinogen compounds

which are complex, condensed, benzene-ring nuclei injurious to tissues

Although N tabacum is a less hardy plant than N rustica, it adapts

itself to a wide variety of climates and soils, and the types generated

in given areas do not normally reproduce the same type in another

area The variety developed in the Near East, known as Turkish

tobacco and valued as an aromatic blend for cigarettes, is a small

plant with numerous leaves only about 3 in (7.6 cm) long, while theAmerican tobaccos grown from the same species have leaves up to 3 ft(0.9 m) long The nicotine content of Turkish tobacco is from 1 to 2%,while that of flue-cured Virginia tobacco is 2.5 to 3%, and that of bur-

ley and fire-cured American types is up to 4.5% Perique, a strong,

black tobacco much used in French and British pipe mixtures, is vated only in a small area of southern Louisiana Other tobaccosbrought into the area become perique in the second year, but when

culti-transplanted back, they do not thrive N rustica was the first tobacco

grown in Virginia, but the tobacco now grown in the area and known

as Virginia tobacco is N tabacum brought from the West Indies, but

now differing in type from West Indian tobacco Makhorka tobacco,

a black, air-cured type grown in Russia and Poland and very high in

nicotine, is from N rustica Strong, black, highly fermented tobaccos

high in nicotine, and considered as inferior in the United States, arepreferred in France and some other countries

Types of tobacco are based on color, flavor, strength, and methods ofcuring and fermentation, while grades are based on size, aroma, andtexture, but the geographical growing area also determines character-istics Commercial purchasing is done by the area and the Department

of Agriculture type classification: fire-cured, dark air-cured, flue-cured,cigar wrapper, cigar binder, cigar filler, burley, Maryland, and perique,

all of which are from N tabacum Grading is done by specialists, and a

single area crop may produce more than 50 grades In the ture of cigarettes, blending is done to attain uniformity, and some of

manufac-the flavor and aroma may be from added ingredients Air-cured

tobaccos are alkaline, while flue-cured tobaccos are acid and the

nicotine is less readily given off N rustica may contain as high as 10%

nicotine and is thus more desirable for insecticide use or for the

extraction of nicotine, but some strains of N tabacum have been

devel-oped for smoking with as little as 0.3% nicotine

Tobacco seed oil has an iodine value of 140 to 146 and is a

valu-able drying oil, but the production is low because the seed heads aretopped in cultivation and seeds are developed only on the sucker

growths Tobacco sauce, used for flavoring chewing and smoking

tobaccos, contains up to 10% nicotine, but since the nicotine is notdesired in the flavoring, it is usually extracted for industrial use

Nicotine can be oxidized easily to nicotinic acid and to

nicotinoni-trile, both of which are important as antipellagra vitamins Most of

the nicotine used for insecticide is marketed as nicotine sulfate in

water solution containing 40% nicotine It is used as a sheep dip and

as a contact insecticide Tobacco dust is used for the control of plant

lice Anabasine, obtained in Russia from the Asiatic shrub Anabasis

aphylla, has the same chemical composition as nicotine and is an

iso-mer of nicotine It is marketed in the form of a solution of the sulfate

as an insecticide It can also be obtained from N glauca, a wild tree

tobacco native to Mexico and the southeastern United States, or is

made synthetically under the name of neonicotine.

TOLU BALSAM. A yellowish-brown, semisolid gum with a pleasant

aromatic odor and taste, obtained from the tree Myroxylon mum, or Toluifera balsamum, of Venezuela, Colombia, and Peru It is

balsa-used in medicine, chiefly in cough syrups, and as a fixative in fumes A soft, tenacious, resinous substance that hardens on keeping,

it is a mixture of free cinnamic and benzoic acids Balsam of Peru,

or black balsam, is a reddish-brown, viscous, aromatic liquid from

bark of the tall tree M pereirae of El Salvador It is used in cough

medicines and skin ointments, as an extender for vanilla, and as afixative in perfumes Some white-colored balsam is also obtained from

the fruit of the tree Peru balsam contains benzyl benzoate, benzyl cinnamate, and some vanillin Styrax is an aromatic balsam from

Liquidambar orientalis, and Zanthorrhoea balsams are acaroid

resins from the X australis tree It is used as a perfumery substitute

for Peru balsam and Styrax

TOLUOL Also called toluene, methyl benzene, and methyl

ben-zol A liquid of composition C6H5CH3, resembling benzene but with adistinctive odor It is obtained as a by-product from coke ovens andfrom coal tar It occurs also in petroleum, with from 0.20 to 0.70% inTexas crude oil, which is not sufficient to extract But toluol may beproduced by dehydrogenation of petroleum fractions It is used as asolvent, and for making explosives, dyestuffs, and many chemicals,and in aviation gasoline to improve the octane rating Industriallypure toluol from coal tar distills off between 227 and 235°F (108.6 and112.6°C), and is a water-white liquid with a specific gravity of 0.864 to0.874, flash point 35 to 40°F (2 to 4°C), and freezing point about

139°F (95°C) The fumes are poisonous Nitration grades are atleast 99.9% pure, and are used in synthesizing adhesives, agriculturalchemicals, coatings, and in textiles Such a material is Unocal

Chemicals’ Amsco B&J Brand, from Burdick & Jackson, is

ultra-high purity and contains very low-luminescence impurities for liquidscintillation counters It is also used for dissolving polymers for gelpermeation chromatography, and has low residues in pesticide residue

analyses Monochlorotoluene, used as a solvent for rubber and

syn-thetic resins, is a colorless liquid of composition CH3C6H4Cl, boiling atabout 320°F (160°C) and freezing at 49°F (45°C) T oil is a sulfur

toluene condensation product made under a British patent and used

as a plasticizer for chlorinated rubber Notol No 1, of Neville

Chemical Co., is a coal tar hydrocarbon high in aromatics used as asubstitute for toluol as a lacquer solvent The specific gravity is 0.825

and the boiling point between 177 and 280°F (81 and 138°C) Tollac,

of the same company, is another hydrocarbon substitute for toluol

Methyl cyclohexane, C6H11CH3, is a water-white liquid with a tilling range of 212 to 217°F (100 to 103°C), produced by hydrogenat-ing toluol It is used as a solvent for oils, fats, waxes, and rubbers

dis-Methyl cyclohexanol, C6H10CH3OH, another toluol derivative, isused as a cellulose ester solvent and as an antioxidant in lubricants It

is a straw-colored, viscous liquid distilling between 311 and 356°F (155

and 180°C) Polyvinyl toluene is a methyl form of styrene It is

poly-merized with terphenyl stilbene to form plastic scintillators to countradiation isotopes

TONKA BEAN Called in northeastern Brazil cumarú bean The

ker-nel of the pit of the fruit of the sarrapia tree, Dipteryx odorata or

Coumarouna odorata, of northern South America, used for the

pro-duction of coumarin for flavoring and scenting It has an aroma

resembling vanilla The trees often reach a height of 100 ft (30 m) andbegin to bear in 3 years The fruit is like a mahogany-colored plum,but with a fibrous pulp The pits, or nuts, contain a single shiny, blackseed 1 in (2.5 cm) or longer The chief production is in Venezuela,Brazil, Colombia, Trinidad, and the Guianas The tonka bean from

the tree D oleifera of Central America has an unpleasant odor Before

shipping, the beans are soaked in rum or alcohol to crystallize thecoumarin The ground beans are again soaked in rum, and the aro-matic liquid is used to spray on cigarette tobacco The coumarinextract is also used as a perfume or flavor in soaps, liqueurs, and con-

fectionery The essential oil produced from the seed is called cumarú

oil A substitute for tonka bean is deer’s tongue leaf, which is the

long leaf of the herb Trilisa odoratissima, growing wild on the edges

of swamps from Carolina to Florida The leaf has a strong odor ofcoumarin when dry, and contains coumarin It is used in cigarettemanufacture, in flavoring, and to produce synthetic vanilla It is also

a normal constituent of lavender oil.

TOOL STEELS. Steels used mainly for cutters in machining, ing, sawing, punching, and trimming operations, and for dies,punches, and molds in cold- and hot-forming operations Some arealso occasionally used for nontool applications Tool steels are primar-ily ingot-cast wrought products, although some are now also powder-metal (PM) products Regarding PM products, there are two kinds: (1)mill products, mainly bar, produced by consolidating powder into

shear-“ingot” and reducing the ingot by conventional thermomechanicalwrought techniques, and (2) end-product tools, produced directly frompowder by pressing and sintering techniques There are seven majorfamilies of tool steels as classified by the American Iron and SteelInstitute (AISI): (1) high-speed tool steels, (2) hot-work tool steels, (3)cold-work tool steels, (4) shock-resisting tool steels, (5) mold steels, (6)special-purpose tool steels, and (7) water-hardening tool steels

High-speed tool steels are subdivided into three principal

groups or types: the molybdenum type, designated M1 to M46; the

tungsten type (T1 to T15); and the intermediate molybdenum type(M50 to M52) Virtually all M types, which contain 3.75 to 9.5%molybdenum, also contain 1.5 to 6.75 tungsten, 3.75 to 4.25chromium, 1 to 3.2 vanadium, and 0.85 to 1.3 carbon M33 to M46also contain 5 to 8.25% cobalt; and M6, 12% cobalt The T types,which are molybdenum-free, contain 12 to 18% tungsten, 4 to 4.5chromium, 1 to 5 vanadium, and 0.75 to 1.5 carbon Except for T1,which is cobalt-free, they also contain 5 to 12% cobalt Both M50 andM52 contain 4% molybdenum and 4 chromium; the former also con-tains 0.85% carbon and 1 vanadium, the latter 0.9 carbon, 1.25 tung-sten, and 2 vanadium.

Although the tungsten types were developed first, around the turn

of the century, the molybdenum types, developed in the 1930s whentungsten was scarce, are now by far the most widely used, and many

of the T types have M-type counterparts All of the high-speed toolsteels are similar in many respects They all can be hardened to atleast Rockwell C 63, have fine grain size, and have deep-hardeningcharacteristics Their most important feature is hot hardness: Theyall can retain a Rockwell C hardness of 52 or more at 1000°F (538°C).The M types, as a group, are somewhat tougher than the T type atequivalent hardness; but otherwise, mechanical properties of the twotypes are similar Cobalt improves hot hardness, but at the expense oftoughness Wear resistance increases with increasing carbon andvanadium contents The M types have a greater tendency to decar-burization and, thus, are more sensitive to heat treatment, especiallyaustenitizing Many of the T types, however, are also sensitive in thisrespect, and they are hardened at somewhat higher temperatures.The single T type that stands out today is T-15, which is rated as thebest of all high-speed tool steels from the standpoint of hot hardnessand wear resistance Typical applications for both the M type and Ttype include lathe tools, end mills, broaches, chasers, hobs, millingcutters, planar tools, punches, drills, reamers, routers, taps, andsaws The intermediate M types are used for somewhat similar cut-ting tools but, because of their lower alloy content, are limited to less-severe operating conditions

Hot-work tool steels are subdivided into three principal groups:

(1) the chromium type (H10 to H19), (2) the tungsten type (H21 toH26), and (3) the molybdenum type (H42) All are medium-carbon(0.35 to 0.60%) grades The chromium types contain 3.25 to 5.00%chromium and other carbide-forming elements, some of which, such

as tungsten and molybdenum, also impart hot strength, and dium, which increases high-temperature wear resistance The tung-sten types, with 9 to 18% tungsten, also contain chromium, usually 2

to 4, although H23 contains 12% of each element The one num type, H42, contains slightly more tungsten (6%) than molybde-num (5), and 4 chromium and 2 vanadium Typical applicationsinclude dies for forging, die casting, extrusion, heading, trim, piercing

molybde-and punching, molybde-and hot-shear blades Magnadie, from Latrobe Steel,

is a 5 chromium, air-hardening steel with better toughness than H13steel and comparable elevated-temperature strength and hardness.Toughness ranges from 6 to 10 ft lb (8 to 14 J), tensile yield strengthfrom 160,000 to 200,000 lb/in2 (1100 to 1380 MPa), and Rockwell Chardness from 40 to 48

There are also three major groups of cold-work tool steels: (1)

high-carbon (1.5 to 2.35%); high-chromium (12), which are designatedD2 to D7; (2) medium-alloy air-hardening (A2 to A10), which may con-tain 0.5 to 2.25% carbon, 0 to 5.25 chromium, 1 to 1.5 molybdenum, 0

to 4.75 vanadium, 0 to 1.25 tungsten, and, in some cases, nickel, ganese or silicon, or nickel and manganese; and (3) oil-hardeningtypes (O1 to O7) They are used mainly for cold-working operations,such as stamping dies, draw dies, and other forming tools as well as

man-for shear blades, burnishing tools, and coining tools

Shock-resis-tant tool steels (S1 to S7) are, as a class, the toughest, although

some chromium-type hot-work grades, such as H10 to H13, are what better in this respect The S types are medium-carbon (0.45 to0.55%) steels containing only 2.50 tungsten and 1.50 chromium (S1),only 3.25 chromium and 1.40 molybdenum (S7), or other combina-tions of elements, such as molybdenum and silicon, manganese andsilicon, or molybdenum, manganese, and silicon Typical uses includechisels, knockout pins, screw driver blades, shear blades, punches,and riveting tools

some-There are three standard mold steels: P6, containing 0.10%

car-bon, 3.5 nickel, and 1.5 chromium; P20, 0.35 carcar-bon, 1.7 chromium,and 0.40 molybdenum; and P21, 0.20 carbon, 4 nickel, and 1.2 alu-minum P6 is basically a carburizing steel produced to tool-steel qual-ity It is intended for hubbing—producing die cavities by pressingwith a male plug—then carburizing, hardening, and tempering P20and P21 are deep-hardening steels and may be supplied in hardenedcondition P21 may be carburized and hardened after machining.These steels are tough but low in wear resistance and moderate inhot hardness, P21 being best in this respect All three are oil-harden-ing steels, and they are used mainly for injection and compressionmolds for forming plastics, but they also have been used for die-cast-

ing dies RA40 mold steel, from A Finkl & Sons Co., is a

double-vac-uum-melted, precipitation-hardened grade for 40 Rockwell Chardness that requires no heat treatment and features better

machinability than the P20 grade It contains 3 nickel, 1.5 ganese, 1 copper, 1 aluminum, 0.3 silicon, and 0.15 carbon It can beused at temperatures up to 930°F (500°C) and is recommended formolding plastics and elastomers requiring greater wear resistancethan that of P20.

man-Special-purpose tool steels include L2, containing 0.50 to 1.10%

carbon, 1.00 chromium, and 0.20 vanadium; and L6, having 0.70 bon, 1.5 nickel, 0.75 chromium, and sometimes 0.25 molybdenum L2

car-is usually hardened by water quenching and L6, which car-is hardening, by quenching in oil They are relatively tough and easy tomachine and are used for brake-forming dies, arbors, punches, taps,

deeper-wrenches, and drills The water-hardening tool steels include W1,

which contains 0.60 to 1.40% carbon and no alloying elements; W2,with the same carbon range and 0.25 vanadium; and W5, having 1.10carbon and 0.50 chromium All are shallow-hardening and the leastqualified of tool steels in terms of hot hardness However, they can besurface-hardened to high hardness and thus can provide high resis-tance to surface wear They are the most readily machined tool steels.Applications include blanking dies, cold-striking dies, files, drills,countersinks, taps, reamers, and jewelry dies

Bethlehem Lukens, makes a series of prehardened plate steels, ignated MTD 1 to MTD 4, which are somewhat similar in composition

des-to 41XX chromium-molybdenum steels The 18% nickel maraging

steels, although developed for structural applications, are also used

as die-casting dies and metal- and plastic-forming dies And Teledyne

Vasco makes matrix steels, which are said to be matrix compositions

of M2 and M42 high-speed tool steels with less carbon and alloy tent They are used for extrusion, compacting, and thread-rollingdies, and punches and saw blades Although most die steels arewrought steels and some are made from powder metal, cast steels arealso used for various applications

con-Although many tool steels are typically wrought products, ers have turned increasingly to the use of powder metals for the start-

produc-ing stock PM tool steels pertain mainly to high-speed grades for

cutting, or machining, applications but several grades for formingapplications are also made from powder Advantages attributed to the

PM steels stem largely from improved microstructural control forcompositional uniformity and freedom from segregation They canprovide superior machinability in the annealed condition, bettergrindability in the hardened and tempered condition without loss ofabrasion resistance, greater toughness, better dimensional stability

in heat treatment, and amenability to high alloy content to promotewear resistance and increase cutting or forming performance

PM tool steels include the Micro-Melt alloys from Carpenter Technology and the CPM alloys from Crucible Materials Corp.

Micro-Melt alloys include AISI standard grades A11, M3, M4, M42,M48, and T15 plus specials like Micro-Melt 9 and 10, HS-30, andMaxamet Alloys 9 and 10 are high-vanadium (8.75 and 9.75%,respectively), tungsten- and cobalt-free, 5.25 chromium, molybdenum

(1.35 and 1.3%), and carbon (1.75 and 2.45%) steels HS-30 tool steel

contains 8.5 cobalt, 6.25 tungsten, 5 molybdenum, 4.2 chromium, 3.1

vanadium, and 1.27 carbon Maxamet tool steel, with 1.3 tungsten,

9 cobalt, 6 vanadium, 5 chromium, and 2.15 carbon, attains 70Rockwell C hardness, and cutting tools made of the steel canapproach the cutting speeds of carbide tools Similarly, CPM gradescan pertain to standard grades, for example, M3, M4, M48, M62, and

T15, or to specials such as CPM Rex grades, CPM 3V to 18V, Vanadis

tool steels, and K190 PM tool steel V grades include both hot- and

cold-work types CPM Rex 121 tool steel, the highest-carbon (3.4%)

CPM tool steel, contains 10.5 tungsten, 9.5 vanadium, 9.5 cobalt, 5.5molybdenum, and 4 chromium It can attain 70 to 72 Rockwell Chardness, and features excellent temper resistance and hot hardness

to 1200°F (650°C) and superior resistance to abrasive and adhesivewear At this hardness, the steel contains about 29% (by volume) pri-mary carbides, mainly the vanadium-rich MC kind for maximumwear resistance It is intended primarily for cutters performing high-speed machining operations

To prolong tool life, tool-steel end products, such as mills, hobs,drills, reamers, punches, and dies, can be nitrided or coated in several

ways Oxide coatings, imparted by heating to about 1050°F (566°C)

in a steam atmosphere or by immersion in aqueous solutions ofsodium hydroxide and sodium nitrite at 285°F (140°C), are not aseffective as traditional nitriding, but do reduce friction and adhesionbetween the workpiece and tool The thickness of the coating devel-oped in the salt bath is typically less than 0.0002 in (0.005 mm), andits nongalling tendency is especially useful for operations in which

failure occurs in this way Hard-chromium plating to a thickness of

0.0001 to 0.0005 in (0.0025 to 0.0127 mm) provides a hardness ofDPH 950 to 1,050 and is more effective than oxide coating, but theplate is brittle and, thus, not advisable for tools subject to shockloads Its toughness may be improved somewhat without substan-tially reducing wear resistance by tempering at temperatures below500°F (260°C), but higher tempering temperatures impair hardness,

thus wear resistance, appreciably An antiseize iron sulfide coating

can be applied electrolytically at 375°F (191°C) using a bath ofsodium and potassium thiocyanate Because of the low temperature,

the tools can be coated in the fully hardened and tempered condition

without affecting hardness Tungsten carbide is another effective

coating One technique, developed by Rocklin Manufacturing and

called Rocklinizing, deposits 0.0001 to 0.0008 in (0.0025 to 0.0203

mm) of the carbide using a vibrating arcing electrode of the material

in a handheld gun Titanium carbide and titanium nitride are the

latest coatings The nitride, typically 0.0003 in (0.008 mm) thick, hasstirred the greatest interest, although the carbide may have advan-tages for press tools subject to high pressure In just the past fewyears, all sorts of tools, primarily cutters but also dies, have been tita-nium-nitride-coated, which imparts a gold- or brasslike look The

coating can be applied by chemical vapor deposition (CVD) at

1750 to 1950°F (954 to 1066°C) or by physical vapor deposition

(PVD) at 900°F (482°C) or less Thus, the PVD process has an

advan-tage in that the temperature involved may be within or below thetempering temperature of the tool steels so that the coating can beapplied to fully hardened and tempered tools Also, the risk of distor-tion during coating is less Titanium nitride coaters includeAerobraze, Multi-Arc Vacuum Systems, Scientific Coatings, StarCutter, Sylvester, and Ti-Coating Another method being used to pro-long tool life is to subject the tools to a temperature of 320°F(196°C) for about 30 h The cryogenic treatment, which has been

called Perm-O-Bond and Cryo-Tech by Materials Improvement, is

said to rid the steel of any retained austenite—thus the improved toollife Others in this business include Amcry, Endure, and 3XKryogenics

TRAGACANTH GUM. An exudation of the shrub Astragalus gummifer

of Asia Minor and Iran, used in adhesives or for mucilage, for leatherdressing, for textile printing, and as an emulsifying agent To obtain thegum, a small incision is made at the base of the shrub, from whichthe juice exudes and solidifies into an alteration product, not merely thedried juice The gum derived from the first day’s incision, known as

fiori, is the best quality and is in clear, fine ribbons or white flakes The

second incision produces a yellow gum known as biondo The third incision produces the poorest quality, a dark gum known as sari Rainy

weather during the incision period may cause a still inferior product.Tragacanth is insoluble in alcohol but is soluble in alkalies and swells

in water Karaya gum from southern Asia is from various species of

Sterculia trees, especially S urens, of India It is also known as

Indian gum, Indian hog gum, and hog tragacanth The sticky

gum is dried, and the chunks are broken and the pieces sorted bycolor A single chunk may have colors varying from clear white to darkamber and black The color is caused by tannin or other impurities

The No 3 grade, the lowest, has up to 3% insoluble impurities Thegum is marketed in flakes and as a white, odorless, 150-mesh powder.The chief constituent is galactan In general, the gum is more acidthan tragacanth and is likely to form lumpy gels unless finely ground.

It is widely used as a thickening and suspending agent for foodstuffs,drugs, cosmetics, adhesives, and textile finishes Gum tragacynth

thoroughly mixed with glycerin and water produces a thick paste,

tra-gacynth glycerite, a useful excipient to bind tablet masses For oral

ingestion, suspensions of gum tragacynth have been formulated One

such product is a suspension of procaine penicillin In hair lotion in

which there is 10% isopropanol, gum tragacynth is able to withstandthe alcohol without precipitation It is also a thickener of the aqueousphase in oil-in-water systems, resulting in shelf-stable emulsions

Regular as well as low-calorie salad dressings, such as Thousand

Island, French, and Roquefort, are such oil-in-water emulsions.

The low-calorie versions have higher amounts of gum tragacynth, toprovide the body that oil traditionally gives the regular dressing

Tragacynth gums, Type A.10, Type W, and Type L, are

pharmaceuti-cal grades in powder form, produced by Meer Corp

The granules of water-soluble gums, such as karaya, tragacanth,

and acacia, are swelled by water and dispersed in water in scopic particles to form cells or filamentlike structures which hold thewater like a sponge and will not settle out This type of colloidal dis-

micro-persion is called a hydrasol, and when thick and viscous is called a

gel From 2 to 3% of karaya or other gum will form a gel in water.

These gums will gel in cold water, while gelatin requires hot water fordissolving In a gel there is continuous structure with molecules form-

ing a network, while in a sol the particles are in separate suspension

and a sol is merely a dispersion Some dispersions, such as albumen,cross-link with heat; others, like guar gum, cross-link with alkalies;still others, like pectin, link with sugar and an acid Gums with weak

surface forces form weak gels which are pastes or mucilage, and a

high concentration is needed to produce a solid Karaya has great

swelling power, and is used in medicine as a bulk laxative Ghatti

gum, from the abundant tree Anogeissus latifolia of India, is entirely

soluble in water to form a viscous mucilage It is twice as effective asgum arabic as an emulsifier, but is less adhesive It comes in colorless

to pale-yellow tears of vitreous fracture, called also Indian gum, and

is used in India for textile finishing Aqualized gum, of Glyco

Products Co., Inc., is tragacanth or karaya chemically treated to givemore rapid solubility Water-soluble gums are also produced syntheti-

cally Polyox gum, of Union Carbide Chemicals Co., is a polymer of

polyethylene oxide containing carboxylic groups giving water ity when the pH is above 4.0 In paper coating with ammonia, the

ammonia evaporates to leave a water-insoluble, grease-resistant filmthat is heat-sealing It is also used in latex paints and in cosmetics.Another water-soluble gum which forms a true gel with a continuous

branched-chain molecular network is okra gum, produced as a

200-mesh tan powder It is edible and is used for thickening and stabilizingfoods and pharmaceuticals It is also used in plating baths for bright-ening nickel, silver, and cadmium plates It is extracted from the pods

of the okra, Hibiscus esculentus, a plant of the cotton family In the

southern states the pods, called gumbo, are used in soups The refined

gum, after extraction of the oils and sugars, contains 40.4% carbon, 6.1hydrogen, and 2.1 nitrogen, with the balance insoluble cellulose

TRIPOLI. A name given to finely granulated, white, porous, siliceousrock, used as an abrasive and as a filler True tripoli is an infusorial,

diatomaceous earth known as tripolite, and is a variety of opal, or

opaline silica In the abrasive industry it is called soft silica It is

quarried in Missouri, Illinois, eastern Tennessee, and Georgia.Pennsylvania rottenstone is not tripoli, although it is often classifiedwith it The material marketed for oil-well drilling mud under the

name of Opalite, is an amorphous silica The Missouri tripoli ranges

in color from white to reddish, and the crude rock has a porosity of45% and contains 30% or more of moisture It is air-dried and thencrushed and furnace-dried Tripoli is used in massive form for themanufacture of filter stones for filtering small supplies of water.Missouri tripoli is also used for the manufacture of foundry parting.Finely ground tripoli, free from iron oxide, is used as a paint filler and

in rubber The grade of tripoli known as O.G (once ground) is used forbuffing composition, D.G (double ground) for foundry partings, andthe air-float product for metal polishes Tripoli grains are soft, porous,and free from sharp cutting faces, and they give a fine polishing

effect It is the most commonly used polishing agent The word silex,

which is an old name for silica and is also used to designate the verized flint from Belgium, is sometimes applied to finely groundwhite tripoli employed as an inert filler for paints Much Illinois fine-grained tripoli is used for paint, and for this purpose it should be free

pul-from iron oxide Rottenstone is a soft, friable, earthy stone of light

gray to olive color, used as an abrasive for metal and wood finishing

It resembles Missouri tripoli and is derived from the weathering ofsiliceous-argillaceous limestone, with generally from 80 to 85% alu-mina, 4 to 15 silica, and 5 to 10 iron oxides Rottenstone was largelyimported from England, but one variety is found in Pennsylvania It

is finely ground and is marketed either as a powder or molded intobricks The latter form is used with oil on rag-wheel polishing A250-mesh powder is used as a filler in molding compounds

TRISODIUM PHOSPHATE. A white, crystalline substance of tion Na3PO4 12H2O, also known as phosphate cleaner, used in

composi-soaps, cleaning compounds, plating, textile processing, and boilercompounds The commercial grade is not less than 97% pure, withtotal alkalinity of 16 to 19% calculated as Na2O The anhydroustrisodium phosphate is 2.3 times as effective as the crystalline form,

but requires a longer time to dissolve Disodium phosphate is a

white, crystalline product of composition Na2HPO4 12H2O used forweighting silk, boiler treatment, cheese making, and cattle feeds.The medicinal, or USP, grade has only seven molecules of water andhas a different crystal structure The commercial grade is 99.4%

pure and is readily soluble in water Trisodium phosphate

hemi-hydrate is a granular, crystalline grade from FMC Corp for

degreasing and water conditioning Monosodium phosphate is

made by reacting soda ash with phosphoric acid in molecular portions; it is used in similar applications to the disodium variety

pro-Sodium tetraphosphate, Na6P4O13, contains 39.6% Na2O and 60.4

P2O5 It is the sodium salt of tetraphosphoric acid and is

mar-keted in beads that are mildly alkaline and highly soluble in water.The specific gravity is 2.55 and it melts at 1,112°F (600°C) It isused in the textile industry as a water softener and to acceleratecleansing operations It removes lime precipitation and sludge and

saves soap Quandrafos, of American Cyanamid Co., used to

replace quebracho for reducing the viscosity of oil-well drilling mud,

is sodium tetraphosphate, containing 63.5% P2O5 It makes the cium and magnesium compounds inactive, and 0.06% of the mater-ial controls 16.1% of water in reducing viscosity It also gives smoothflow with minimum water in paper coating and textile printing

cal-Metafos, of the same company, has a higher percentage of P2O5—67%—and a lower pH, for use in textile printing where low alkalin-

ity is needed Sodium pyrophosphate, Na4P2O7, is added to soappowders to increase the detergent effect and the lathering It is alsoused in oil-drilling mud The crystalline form, Na4P2O7 10H2O, isvery soluble in water and is noncaking, and it is used in household

cleaning compounds Sodium tripolyphosphate, Na5P3O10, is awater-soluble, white powder used as a detergent, a water softener,and a deflocculating agent in portland cement to govern the viscos-ity of the shale slurry without excessive use of water Large quanti-ties of these phosphates are used in the processing of chemicals,textiles, and paper; and since they are toxic contaminants of groundand surface waters, mill wastes must be deactivated before they aredischarged The use of phosphates in detergents and soap powdershas been banned in many areas since they lead to rapid algalgrowth in surface waters

TULIPWOOD Also called yellow poplar, whitewood, and canary

whitewood, the wood of the tree Liriodendron tulipifera of Canada

and the eastern United States The tree grows to a height of 250 ft(76 m) and to diameters of more than 10 ft (3 m) It is used for furni-ture, veneer, millwork, toys, woodenware, boxes, crates, and pulp-wood Owing to its close texture and even coefficient of expansion, ithas been used for expansion blocks in humidity regulators It is yel-lowish, soft, and durable The density is about 30 lb/ft3 (481 kg/m3)

The lumber may be mixed with cucumber magnolia, Magnolia acuminata, and evergreen magnolia, M grandifolia, but magnolia

woods are lighter in color.

TUNG OIL. A drying oil which has almost double the rapidity of seed oil It is used for enamels and varnishes; in brake linings, plasticcompounds, and linoleum; and for making pigment for India ink

lin-Tung oil is pressed from the seeds of Aleurites montana and A fordii.

The names wood oil and China wood oil are loosely and

erro-neously used to designate tung oils, but true wood oil is an oleoresin

from the Keruing tree of Malaya used for waterproofing and

caulk-ing boats, while tung oil is never from the wood The oil has a ful purgative action, and the Chinese word means stomach The

power-Chinese tung oil is from the nuts of the tree A montana, the China

wood oil tree, and A fordii The latter tree is hardier than A tana, which requires a hot climate The American tung oil is from the nuts of the tree A fordii of the Gulf states, which gives an annual

mon-production of about 30 lb (14 kg) of oil per tree The tree grows to aheight of 25 ft (8 m) and bears for 5 years The seeds, or nuts, contain

50 to 55% oil This tree is also grown in South Africa and Argentina.The color of tung oil varies from golden yellow to dark brownaccording to the degree of heat used in extraction It has a pungentodor resembling that of bacon fat A good grade of raw tung oil shouldhave a specific gravity between 0.934 and 0.940, a saponificationvalue of 190, and an iodine value of 163 The oil contains about 72%

eleostearic acid, which has a very high iodine value, 274, and gives

to the oil a greater drying power than is indicated by the iodine value

of the oil itself The oil has the property of drying throughout at auniform rate, instead of forming a skin as linseed oil does; but it driesflat instead of glossy, like linseed oil, and is inclined to produce awrinkled surface It is mixed with rosin, since rosin has great affinityfor it, and the two together are suitable for gloss varnishes In combi-nation with other drying oils, it improves water and alkali resistance,and is used mainly in quick-drying enamels and varnishes The oil

from A montana, or mu oil, has a higher percentage of eleostearic acid than that from A fordii The Japanese tung oil is from the

nuts of the larger tree A cordata The oil is superior to Chinese tung

oil and is seldom exported It does not gelatinize as Chinese tung oildoes, when heated It is used in Japan for varnishes, waterproofingpaper, and soaps The saponification value is 193 to 195, iodine value

of 149 to 159, and specific gravity 0.934 to 0.940 The kernels of thenuts yield about 40% oil The tree is grown also in Brazil and thrives

in hot climates Candlenut oil is from the seed nuts of A moluccana

of Oceania and southern Asia It received its name from the fact thatthe Polynesians used the nuts as candles to light their houses The oil

is variously known as kukui, kekune, and lumbang, and as an artist’s paint, oil is called walnut oil or artist’s oil The nut resem-

bles the walnut but has a thicker shell The oil has a specific gravity

of 0.923, iodine value 165, and is between linseed and soybean oil inproperties It is high in linoleic and linolenic acids The variety

known as soft lumbang oil, or bagilumbang oil, from the tree A.

trisperma of the Philippines, resembles tung oil and is high in

eleostearic acid The chief production of lumbang oil is in the FijiIslands

The Safflower, Carthamus tinctorius, is grown in California,

France, and India, and in the latter country it is grown on a large

scale for seeds, which yield up to 35% of the clear, yellowish

saf-flower oil used in paints, leather dressings, in the manufacture of

nonyellowing alkyd resins, and for foods The oil has a high content,73%, of linoleic acid, the highest of essential polyunsaturated acids ofany vegetable food oil It is odorless, with a bland taste, has a specific

gravity of 0.915, and an iodine value of 150 Safflower 22, of Pacific

Vegetable Oil Corp., is a conjugated paint oil made by isomerizing flower oil It has a rapid drying rate, color retention, and an ability toproduce wrinkled finishes by adjustment of the amount of drier Itcan thus replace tung oil It takes up maleic anhydride readily, and is

saf-used for making modified alkyd finishes Wecoline SF, of Drew

Chemical, is a concentrate of safflower fatty acids with 67.3% linoleic

acid and only 0.2 linolenic acid, for compounding in coatings Saff, of

Abbott Laboratories, is an emulsion of safflower oil used as a drug tolower blood cholesterol Refined and deodorized oil shows 2.8  106

lb (1.3 mg) of “cholesterol-equivalent” sterols per 0.22 lb (100 g) of oil.The heads of the plant are dried and used as food colors, for dyeingtextiles, and for cosmetic rouge

TUNGSTEN AND TUNGSTEN ALLOYS. A heavy, white metal, symbol W,with a specific gravity of 19.6, a density of 0.697 lb/in3(19,290 kg/m3),the highest melting point, 6170°F (3410°C), of all metals and a tensilestrength of 50,000 lb/in2 (345 MPa) at 2500°F (1370°C) Wolframite

is the chief ore of the metal tungsten Its composition is (FeMn)WO3

TUNGSTEN AND TUNGSTEN ALLOYS 985

986 TUNGSTEN AND TUNGSTEN ALLOYS

When the manganese tungstate is low, the ore is called ferberite; when the iron tungstate is low, it is called hübnerite The ore is con-

centrated by gravity methods to a concentrate containing 60 to 65%

tungstic oxide, WO3 To extract pure WO3from the concentrate, it isfused with sodium carbonate, Na2CO3, to form sodium tungstate,

Na2WO3, which is dissolved in water When an acid is added to thesolution, the WO3 precipitates out as a yellow powder The metallictungsten is obtained by reduction and is then pressed into bars andsintered Wolframite occurs usually bladed or columnar in form Ithas a specific gravity of 7.2 to 7.5, a Mohs hardness of 5, a black color,and a submetallic luster It is found in the mountain states, Alaska,China, and Argentina, but it also widely distributed in various parts

of the world in small quantities Chinese wolfram concentrates

contain 65% tungstic oxide; the Arizona concentrates contain an age of 67% California and Nevada concentrates are scheelite contain-

aver-ing from 60 to 67% tungstic oxide The sanmartinite of Argentina is

a variety containing zinc

Tungsten has a wide usage in alloy steels, magnets, heavy metals,electric contacts, rocket nozzles, and electronic applications It is alsoused for x-ray and gamma-ray shielding and wear-resistant surfaces,electroplates providing Vickers 700 or greater hardness Tungstenresists oxidation at very high temperatures and is not attacked bynitric, hydrofluoric, or sulfuric acid solutions Flame-sprayed coatingsare used for nozzles and other parts subject to heat erosion

Tungsten alloys are used for weights and counterbalances, radiation

shielding, grinding tools, tooling, and high-temperature applications

Copper-tungsten composites and silver-tungsten composites

serve as resistance-welding die inserts, electrode facings, electricalcontacts, heat sinks, wear surfaces, and electrodes for electrical-dis-charge machining (EDM) and electrochemical machining

Tungsten is usually added to iron and steel in the form of

ferro-tungsten, made by electric-furnace reduction of the oxide with iron or

by reducing tungsten ores with carbon and silicon Standard gradeswith 75 to 85% tungsten have melting points from 3200 to 3450°F

(1760 to 1899°C) Tungsten powder is usually in sizes from 200 to

325 mesh, and may be had in a purity of 99.9% Parts, rods, and sheetare made by powder metallurgy, and rolling and forging are done athigh temperature The rolled metal may have a tensile strength ashigh as 500,000 lb/in2 (3,448 MPa) and a Brinell hardness of 290,whereas drawn wire may have a tensile strength to 590,000 lb/in2

(4,068 MPa) The tungsten powder is used for spray coatings for

radia-tion shielding and for powder-metal parts Tungsten wire is used for spark plugs and electronic devices, and tungsten filaments are used

in lamps Tungsten wire as fine as 0.00018 in (0.00046 cm) is used in

TUNGSTEN AND TUNGSTEN ALLOYS 987

electronic hardware, and as thin as 0.0004 in (0.001 cm) for wire

EDM Tungsten whiskers, which are extremely fine fibers, are used

in copper alloys to add strength Copper wire, which normally has atensile strength of 30,000 lb/in2 (207 MPa), will have a strength of120,000 lb/in2 (827 MPa) when 35% of the wire is tungsten whiskers

Tungsten yarns are made up of fine fibers of the metal The yarns

are flexible and can be woven into fabrics Continuous tungsten ments, usually 394 to 591
in (10 to 15
m) in diameter, are used forreinforcement in metal, ceramic, and plastic composites Finer fila-

fila-ments are used as cores, or substrates, for boron filafila-ments.

The metal is also produced as arc-fused grown crystals, usually nolarger than 0.375 in (0.952 cm) in diameter and 10 in (25.4 cm) long,

and worked into rod, sheet, strip, and wire Tungsten crystals,

99.9975% pure, are ductile even at very low temperatures, and wire

as fine as 0.003 in (0.008 cm) and strip as thin as 0.005 in (0.013 cm)can be cold-drawn and cold-rolled from the crystal The crystal metalhas nearly zero porosity, and its electrical and heat conductivities arehigher than those of ordinary tungsten The normal electrical conduc-tivity is about 33% that of copper, but that of the crystal is 15%higher The molecules of tungsten appear as body-centered cubes, but

in the pure metal the atoms normally bond uniformly in six tions, forming a double lattice so that each grain forms a true singlecrystal At elevated temperatures, tungsten forms many compounds

direc-in chemicals and alloys One tungsten-alumdirec-inum alloy is a

chemi-cal compound made by reducing tungsten hexachloride with molten

aluminum Tungsten-rhenium alloys, in wire, rod, sheet, and plate

from Rhenium Alloys, Inc., include tungsten-26 rhenium, tungsten-25rhenium and tungsten-5 rhenium The W-25Re alloy has a density of0.711 lb/in3(19,680 kg/m3) and melts at 5522°F (3050°C) The electri-cal conductivity is 6% IACS, the ultimate tensile strength is 225,000lb/in2 (1,551 MPa), the elongation is 10%, and the tensile modulus is59,460,000 lb/in2(410,000 MPa)

Mi-Tech Metals Inc produces series of tungsten-based metals or

alloys for various requirements The HD tungsten Series, for

high-density, high-strength applications, contains 90 to 97% tungsten, plusnickel, iron, or copper, or iron and molybdenum Depending on grade,density ranges from 0.614 to 0.668 lb/in3 (17,000 to 18,500 kg/m3),hardness is 24 to 32 Rockwell C, ultimate tensile strength is 110,000

to 125,000 lb/in2 (758 to 862 MPa), tensile yield strength is 80,000 to95,000 lb/in2 (552 to 655 MPa), and elongation is 4 to 10% Also, thetensile modulus is 40  106 to 53  106 lb/in2 (276,000 to 365,000MPa), electrical conductivity is 13 to 17%, and most grades areslightly magnetic Typical uses include crankshaft balancing, radia-tion shielding, rotating inertia members, ordnance parts, boring bars

988 TUNGSTEN CARBIDE

and grinding quills and dies for die casting, extrusion, and hot

upset-ting A CW tungsten-copper Series, with 68 to 80% tungsten and

the balance copper, is used for electrical-discharge and cal machining Another, 74 tungsten-26 silver, is also used for EDM.Tungsten-copper grades, with 28 to 55% electrical conductivity, areused for resistance welding, resistance-welding electrode facings,flash-butt-welding dies, and hot upsetting dies Other metals made by

electrochemi-the company are copper– or copper alloy–tungsten carbide and

Elecon tungsten-copper and tungsten-silver, tungsten

carbide–silver, and molybdenum-silver electrical contact metals There’s also the Thermitech tungsten-copper Series for heat-sink

applications

Cobalt-tungsten alloy, with 50% tungsten, gives a plate that

retains a high hardness at red heat Tungsten RhC is a

tungsten-rhenium carbide alloy containing 4% tungsten-rhenium carbide It is used

for parts requiring high strength and hardness at high temperatures.The alloy retains a tensile strength of 75,000 lb/in2 (517 MPa) at

3500°F (1927°C) Ammonium metatungstate, used for

electroplat-ing, is a white powder of composition (NH4)6H2W12O40 It is readilysoluble in water and gives solutions of 50% tungsten content

Tungsten hexafluoride is used for producing tungsten coatings by

vapor deposition At a temperature of 900°F (482°C) the gas mixed

with hydrogen deposits a tungsten plate Tungsten hexachloride,

WCl6, is also used for depositing tungsten coatings at that ture in a hydrogen atmosphere Smooth, dense tungsten plates can

tempera-be deposited from tungsten carbonyl, W(CO)6, at a temperature of302°F (150°C) The carbonyl is made by reacting the hexachloridewith carbon monoxide

TUNGSTEN CARBIDE. An iron-gray powder of minute cubical crystalswith a Mohs hardness above 9.5 and a melting point of about 5400°F(2982°C) It is produced by reacting a hydrocarbon vapor with tung-sten at high temperature The composition is WC, but at high heat itmay decompose into W2C and carbon, and the carbide may be a mix-ture of the two forms Other forms may also be produced, such as W3Cand W3C4 Tungsten carbide is used chiefly for cutting tool bits andfor heat- and erosion-resistant parts and coatings

Briquetting of tungsten carbide into usable form was firstpatented in Germany and produced by Krupp Works under the

name of Widia metal It is made by diffusing powdered cobalt

through the finely divided carbide under hydraulic pressure, andthen sintering in an inert atmosphere at about 2732°F (1500°C).The briquetted material is ground to shape, and the pieces arebrazed into tools They withstand cutting speeds from 3 to 10 times

those of high-speed steel, and will turn manganese steel with aBrinell hardness of 550, but are not shock-resistant Pressed andsintered parts usually contain 3 to 20% cobalt binder, but nickelmay also be used as a binder The compressive strengths may be ashigh as 700,000 lb/in2 (4,827 MPa) with rupture strengths to200,000 lb/in2(1,379 MPa) or higher.

One of the earliest of the U.S bonded tungsten carbides was

Carboloy, of General Electric Co., used for cutting tools, gages,

drawing dies, and wear parts The sintered materials have been

sold under many trade names such as Dimondite, Firthite, and

Firthaloy; Armide, of Armstrong Bros Tool Co.; Wilcoloy; and Borium and Borod, of Stoody Co But the carbides are now often

mixed carbides Carboloy 608 contains 83% chromium carbide, 2

tungsten carbide, and 15 nickel binder It is lighter in weight thantungsten carbide, is nonmagnetic, and has a Rockwell A hardness to

93 It is used for wear-resistant parts and resists oxidation to2000°F (1092°C) Titanium carbide is more fragile, but may be

mixed with tungsten carbide to add hardness for dies Cutanit is such a mixture Kennametal K601, of Kennametal, Inc., for seal

rings and wear parts, is a mixture of tantalum and tungsten bides without a binder It has a compressive strength of 675,000lb/in2 (4,654 MPa), rupture strength of 100,000 lb/in2 (690 MPa),

car-and Rockwell A hardness of 94 Kennametal K501 is tungsten

carbide with a platinum binder for parts subject to severe heat

ero-sion Strauss metal, of Allegheny Ludlum Steel Co., is tungsten carbide Tungsten carbide LW-1 is tungsten carbide with about

6% cobalt binder used for flame-coating metal parts to give temperature wear resistance Deposited coatings have a Vickers

high-h a r d n e s s t o 1 , 4 5 0 a n d r e s i s t o x i d a t i o n a t 1 0 0 0 ° F ( 5 3 8 ° C )

Tungsten carbide LW-1N, with 15% cobalt binder, has a much

higher rupture strength, but the Vickers hardness is reduced to

1,150 Metco 35C is a fine powder of tungsten carbide and cobalt

for flame spraying to produce a wear-resistant coating of carbide in

a matrix of cobalt GPX 9660, of Securamax International, is a

tungsten carbide and cobalt coating applied by flame spraying toincrease the wear resistance and, to some extent, the corrosionresistance of steel parts A tungsten carbide and nickel formula-

tion, GPX 9657, also increases wear resistance and provides better

corrosion resistance Tungsten carbide chemically bonded to a ified nickel aluminide, developed at the U.S Department ofEnergy’s Oak Ridge National Laboratory and patented by DowChemical and Martin Marietta Energy Systems, is harder and perhapsmore durable than tungsten carbide–cobalt in rock-, coal-, andmetal-cutting applications

TUNGSTEN STEEL. Any steel containing tungsten as the alloying ment imparting the chief characteristics to the steel It is one of theoldest of the alloying elements in steel, the celebrated ancientEastern sword steels having contained tungsten Tungsten increasesthe hardness of steel, and gives it the property of red hardness, stabi-lizing the hard carbides at high temperatures It also widens thehardening range of steel and gives deep hardening Very small quan-tities serve to produce a fine grain and raise the yield point Thetungsten forms a very hard carbide and an iron tungstite, and thestrength of the steel is also increased, but it is brittle when the tung-sten content is high When large percentages of tungsten are used insteel, they must be supplemented by other carbide-forming elements.Tungsten steels, except the low-tungsten chromium-tungsten steels,are not suitable for construction; but they are widely used for cuttingtools, because the tungsten forms hard, abrasion-resistant particles inhigh-carbon steels Tungsten also increases the acid resistance andcorrosion resistance of steels The steels are difficult to forge and can-not be readily welded when tungsten exceeds 2% Standard

ele-tungsten-chromium alloy steels 72XX contain 1.5 to 2% tungsten

and 0.50 to 1 chromium Many tool steels rely on tungsten as analloying element, and it may range from 0.50 to 2.50% in cold-workand shock-resisting types to 9 to 18 in the hot-work type, and 12 to 20

in high-speed steels

TURPENTINE Also called in the paint industry oil of turpentine.

An oil obtained by steam distillation of the oleoresin which exudeswhen various conifer trees are cut Longleaf pine and slash pine arethe main sources It also includes oils obtained by distillation and sol-vent extraction from stumpwood and waste wood Longleaf sapwoodcontains about 2% oleoresin, heartwood 7 to 10%, and stumpwood25% Most oleoresin is obtained from the sapwood of living trees, but

it is not the sap of the tree Heartwood resin is obtained only whenthe cut wood is treated with solvents The oleoresin yields about 20%

oil of turpentine and 80 rosin; both together are known as naval

camphene Some wood turpentine is produced as a by-product in the

manufacture of cellulose Sulfate turpentine is a by-product in the

making of wood pulp It varies in composition as the less stable betapinene is affected by the pulping process, and it is used largely inchemical manufacture By hydrogenation it produces cymene from

which dimethyl styrene is made This material can be

copolymer-ized to produce vinyl resins

Turpentine varies in composition according to the species of pinefrom which it is obtained It is produced chiefly in the United States,

France, and Spain The turpentine of India comes from the chir

pine, Pinus longifolia, of the southern slopes of the Himalayas, also

valued for lumber, and the khasia pine, P khasya The gum of the

chir pine is different from U.S gum, and the turpentine, unless fully distilled, is slower-drying and greasy French and Spanish tur-

care-pentine, or Bordeaux turcare-pentine, is from the maritime pine, P pinaster, which is the chief source, and from Aleppo pine, P halepensis, and Corsican pine, P lavicia In Portugal, the stone

pine, P pinea, is the source The French maritime pine is also grown

on plantations in Australia Aleppo pine of Greece was the source of

the naval stores of the ancients Venetian turpentine, or Venice

turpentine, is from the Corsican pine or European larch It produces

a harder film than U.S turpentine Artificial Venice turpentine ismade by mixing rosin with turpentine European pines do not give ashigh a yield as U.S longleaf and slash pines

American turpentine oil boils at 309°F (154°C), and the specificgravity is 0.860 It is a valuable drying oil for paints and varnishes,owing to its property of rapidly absorbing oxygen from the atmo-sphere and transferring it to the linseed or other drying oil, whichleaves a tough and durable film of paint Turpentine is also used inthe manufacture of artificial camphor and rubber, and in linoleum,

soap, and ink Gum thus, used in artists’ oil paints, is thickened

tur-pentine, although gum thus was originally made from olibanum.Turpentine is often adulterated with other oils of the pine or withpetroleum products, and the various states have laws regulating itsadulteration for paint use

The pinene in European turpentine is levorotatory while that in the United States is dextrorotatory Pinonic acid is acetyl dimethyl

cyclobutane acetic acid It is produced by oxidation of the pinene and

is a white powder used as a cross-linking agent for making ble plastics

heat-sta-Terpene alcohol, or methylol pinene, C11H17OH, is produced bycondensing the beta pinene of gum turpentine with formaldehyde

Nopol, of Glidden Co., is terpene alcohol It has the chemical

reac-tions of both a primary alcohol and pinene, and it is used in making

many chemicals It is a water-insoluble liquid of specific gravity

0.963, boiling at 455°F (235°C) Terpineol is a name for refined

ter-pene alcohols used largely for producing essential oils and perfumes

Piccolyte resin is a terpene thermoplastic varnish resin made from

turpentine The grades have melting points from 50 to 257°F (10 to

125°C) Myrcene is a polyolefin with three double bonds, which can

be used as a substitute for butadiene in the manufacture of syntheticrubbers, or can be reacted with maleic anhydride or dibasic acids toform synthetic resins It is made by isomerizing the beta pinene of

gum turpentine Camphene is produced by isomerizing the alpha

pinene of turpentine Camphor is then produced by oxidation of phene in acid Camphene was also the name of a lamp oil of the earlynineteenth century made from distilled turpentine and alcohol Itgave a bright white light, but was explosive The insecticide known as

cam-Toxaphene, of Hercules Inc., is made by chlorinating camphene to

68% chlorine, or to the empirical formula C10H20Cl8 It is a yellow,waxy powder with a piney odor, melting at 149 to 194°F (65 to 90°C)

It is soluble in petroleum solvents

TURQUOISE. An opaque-blue gemstone with a waxy luster It is ahydrous phosphate of aluminum and copper oxides It is found in thewestern United States in streaks in volcanic rocks, but most of theturquoise has come from the Kuh-i-Firouzeh, or turquoise mountain,

of Iran, which is a vast deposit of brecciated porphyry, or feldsparigneous rock The valuable stones are the deep blue The pale blue

and green stones were called Mecca stones because they were sent

to Mecca for sale to pilgrims Bone turquoise, or odontolite, used

for jewelry, is fossil bone or tooth, colored by a phosphate of iron

TYPE METAL. Any metal used for making printing type, but the name

generally refers to lead-antimony-tin alloys Antimony has the

prop-erty of expanding on cooling and thus fills the mold and producessharp, accurate type The properties required in a type metal are abil-ity to make sharp, uniform castings; strength and hardness; fairly lowmelting point; narrow freezing range to facilitate rapid manufacture

in type-making machines; and resistance to drossing A common typemetal is composed of 9 parts lead to 1 antimony, but many varieties ofother mixtures are also used The antimony content may be as high as

30%, 15 to 20% being frequent A common monotype metal has 72%

lead, 18 antimony, and 10 tin Larger and softer types are made ofother alloys, sometimes containing bismuth; the hardest small typecontains 3 parts lead to 1 antimony A low-melting-point, soft-typemetal contains 22% bismuth, 50 lead, and 28 antimony It will melt atabout 310°F (154°C) Copper, up to 2%, is sometimes added to type

metal to increase the hardness, but is not ordinarily used in metalsemployed in rapid-acting type machines Some monotype metal has

about 18% antimony, 8 tin, and 0.1 copper, but standard linotype

metal for pressure casting has 79% lead, 16 antimony, and 5 tin Stereotype metal, for sharp casting and hard-wearing qualities, is

given as 80.0% lead, 13.5 antimony, 6 tin, and 0.5 copper Intertype

metal has 11 to 14% antimony and 3 to 5 tin A typical formula for electrotype metal is 94% lead, 3 tin, and 3 antimony The Brinell

hardness of machine-molded type ranges from 17 to 23, and that ofstereotype metal is up to 30 As constant remelting causes the separa-tion of the tin and lead, and the loss of tin, or impoverishment of themetal, new metal must be constantly added to prevent deterioration of

a standard metal into an inferior alloy For many years mony-tin alloys have been used as a weld seam filler in auto andtruck bodies In this application they are commonly referred to as

lead-anti-body solder Because of advances in printing technology and auto

manufacturing, use of these lead alloys is steadily declining

ULTRAHIGH-STRENGTH STEELS. The highest-strength steels able Arbitrarily, steels with tensile strengths of around 200,000 lb/in2

avail-(1,379 MPa) or higher are included in this category, and more than

100 alloy steels can be thus classified They differ rather widelyamong themselves in composition and/or the way in which the ultra-high strengths are achieved

Medium-carbon, low-alloy steels were the initial

ultrahigh-strength steels, and within this group, a chromium-molybdenum

steel (4130) grade and a chromium-nickel-molybdenum steel

(4340) grade were the first developed These steels have yieldstrengths as high as 240,000 lb/in2(1,655 MPa) and tensile strengthsapproaching 300,000 lb/in2 (2,069 MPa) They are particularly usefulfor thick sections because they are moderately priced and have deep

hardenability Several types of stainless steels are capable of

strengths above 200,000 lb/in2 (1,379 MPa), including a number ofmartensitic, cold-rolled austenitic, and semiaustenitic grades Thetypical martensitic grades are types 410, 420, and 431, as well as cer-

tain age-hardenable alloys The cold-rolled austenitic stainless

steels work-harden rapidly and can achieve 180,000 lb/in2 (1,241MPa) tensile yield strength and 200,000 lb/in2 (1,379 MPa) ultimate

strength Semiaustenitic stainless steels can be heat-treated for

use at yield strengths as high as 220,000 lb/in2(1,517 MPa) and mate strengths of 235,000 lb/in2(1,620 MPa)

ulti-Maraging steels contain 18 to 25% nickel plus substantial

amounts of cobalt and molybdenum Some newer grades containsomewhat less than 10% nickel and between 10 and 14 chromium

ULTRAHIGH-STRENGTH STEELS 993

Because of the low carbon (0.03% maximum) and nickel content,maraging steels are martensitic in the annealed condition, but arestill readily formed, machined, and welded By a simple aging treat-ment at about 900°F (482°C), yield strengths as high as 300,000 and350,000 lb/in2 (2,069 and 2,413 MPa) are attainable, depending onspecific composition In this condition, although ductility is fairly low,the material is still far from being brittle.

Among the strongest of plain carbon sheet steels are the low- and

medium-carbon sheet grades of Inland Steel, called MarTinsite.

Made by rapid water quenching after cold rolling, they provide tensileyield strengths to 220,000 lb/in2 (1,517 MPa) but are quite limited inductility

There are two types of ultrahigh-strength, low-carbon, hardenable

steels One, a chromium-nickel-molybdenum steel, named

Astralloy, with 0.24% carbon is air-hardened to a yield strength of

180,000 lb/in2 (1,241 MPa) in heavy sections when it is normalized

and tempered at 500°F (260°C) The other type is an

iron-chromium-molybdenum-cobalt steel and is strengthened by a

precipitation-hardening and aging process to levels up to 245,000lb/in2 (1,689 MPa) in yield strength High-alloy quenched-and-tem-

pered steels are another group that have extrahigh strengths They

contain 9% nickel, 4 cobalt, and from 0.20 to 0.30 carbon, and developyield strengths close to 300,000 lb/in2 (2,069 MPa) and ultimatestrengths of 350,000 lb/in2 (2,413 MPa) Another group in this high-

alloy category resembles high-speed tool steels, but is modified to

eliminate excess carbide, thus considerably improving ductility These

so-called matrix steels contain tungsten, molybdenum, chromium,

vanadium, cobalt, and about 0.5% carbon They can be heat-treated toultimate strengths of over 400,000 lb/in2 (2,758 MPa)—the higheststrength presently available in steels, except for heavily

cold-worked high-carbon steel strips used for razor blades and

drawn wire for musical instruments, both of which have tensilestrengths as high as 600,000 lb/in2(4,137 MPa)

Aermet 100, of Carpenter Technology, is a nickel and cobalt steel

strengthened by carbon, columbium, and molybdenum Originallydeveloped for aerospace applications, it combines high tensile yieldstrength [(250,000 lb/in2 (1,724 MPa)] and fracture toughness[(115,000 lb/in2 兹in苶 (126 MPa 兹m苶)] Uses include aircraft landinggears, racing-car shafts, racing-bicycle frames, mandrel-supportshafts, punch-base supports, and special bolting systems

URANIUM. An elementary metal, symbol U It never occurs free innature but is found chiefly as an oxide in the minerals pitchblendeand carnotite where it is associated with radium The metal has aspecific gravity of 18.68 and atomic weight 238.2 The melting point is

about 2071°F (1133°C) It is hard but malleable, resembling nickel incolor, but related to chromium, tungsten, and molybdenum It is solu-ble in mineral acids.

Uranium has three forms The alpha phase, or orthorhombic tal, is stable to 1220°F (660°C); the beta, or tetragonal, exists from

crys-1220 to 1400°F (660 to 760°C); and the gamma, or body-centeredcubic, is from 1400°F to the melting point The cast metal has aRockwell B hardness of 80 to 100, work-hardening easily The metal

is alloyed with iron to make ferrouranium, used to impart special

properties to steel It increases the elastic limit and the tensilestrength of steels, and is also a more powerful deoxidizer than vana-dium It will denitrogenize steel and has carbide-forming qualities Ithas been used in high-speed steels in amounts of 0.05 to 5% toincrease the strength and toughness, but because of its importancefor atomic applications its use in steel is now limited to the by-prod-

uct nonradioactive isotope uranium 238 The green salt used in atomic work is uranium tetrafluoride, UF4 Uranium hexafluo-

ride, UF6, is a gas used to separate uranium isotopes

Metallic uranium is used as a cathode in photoelectric tubesresponsive to ultraviolet radiation Uranium compounds, especiallythe uranium oxides, were used for making glazes in the ceramicindustry and also for paint pigments It produces a yellowish-green,fluorescent glass, and a beautiful red with yellowish tinge is produced

on pottery glazes Uranium dioxide, UO2, is used in sintered forms

as fuel for power reactors It is chemically stable and has a high ing point at about 5000°F (2760°C), but a low thermal conductivity.For fuel use the particles may be coated with about 0.001 in (0.003cm) of aluminum oxide This coating is impervious to xenon and otherradioactive isotopes so that only the useful power-providing rays canescape These are not dangerous at a distance of about 6 in (15 cm),and thus less shielding is needed For temperatures above 2300°F(1260°C) a coating of pyrolitic graphite is used

melt-Uranium has isotopes from 234 to 239, and uranium 235, with 92

protons and 143 neutrons, is the one valued for atomic work Thepurified natural metal contains only about one part U235to about 140parts of U238, and about 100,000 lb (45,360 kg) of uranium fluoride,

UF6, must be processed to obtain 1 lb (0.45 kg) of U235F6 Uranium

238, after the loss of three alpha particles of total mass 12, changes to radium 226 The lead of old uranium minerals came from Ra226 by

the loss of five alpha particles, and is lead 206, while the lead in rium metals is lead 208 Lead 207 comes from the decay of actinum

tho-and exists only in small quantities

Natural uranium does not normally undergo fission because of thehigh probability of the neutron being captured by the U238which thenmerely ejects a gamma ray and becomes U239 When natural uranium

is not in concentrated form, but is embodied in a matrix of graphite orheavy water, it will sustain a slow chain reaction sufficient to produceheat In the fission of U235, neutrons are created which maintain thechain reaction and convert U238 to plutonium About 40 elements ofthe central portion of the periodic table are also produced by the fis-sion, and eventually these products build up to a point where thereaction is no longer self-sustaining The slow, nonexplosive disinte-

gration of the plutonium yields neptunium Uranium 233 is made by

neutron bombardment of thorium This isotope is fissionable and isused in thermonuclear reactors

Uranium yellow, also called yellow oxide, is a sodium ranate of composition Na2U2O7 6H2O, obtained by reduction andtreatment of the mineral pitchblende It is used for yellow and green-ish glazing enamels and for imparting an opalescent yellow to glass,

diu-which is green in reflected light Uranium oxide is an olive-green

powder of composition U3O8, used as a pigment Uranium trioxide,

UO3, is an orange-yellow powder also used for ceramics and pigments

It is also called uranic oxide As a pigment in glass, it produces a beautiful greenish-yellow uranium glass Uranium pentoxide,

U2O5, is a black powder, and uranous oxide, UO2, is used in glass to

give a fine black color Sodium uranate, Na2UO4, is a yellow toorange powder used to produce ivory to yellow shades in potteryglazes The uranium oxide colors give luster and iridescence, butbecause of the application of the metal-to-atom work, the uses in pig-ments and ceramics are now limited

URANIUM ORES The chief source of radium and uranium is

urani-nite, or pitchblende, a black, massive or granular mineral with

pitchlike luster The mineral is a combination of the oxides of nium, UO2, UO3, and U3O8, together with small amounts of lead, tho-rium, yttrium, cerium, helium, argon, and radium The process ofseparation of radium is chemically complicated Uraninite is foundwith the ores of silver and lead in central Europe In the United States

ura-it occurs in pegmatura-ite veins, in the mica mines of North Carolina, and

in the carnotite of Utah and Colorado The richest ores come from theCongo and from near Great Bear Lake, Canada About 370 tons (336metric tons) of Great Bear Lake ore produces 0.002 lb (1 g) of radiumand 7,800 lb (3,538 kg) of uranium, and small amounts of polonium,ionium, silver, and radioactive lead Numerous minor uranium oresoccur in many areas A low-grade ore of 0.1% U3O8can be upgraded to

as high as 5% by ion exchange Black mud from the fjords of Norwaycontains up to 2 oz (0.06 kg) of uranium per long ton (1 metric ton)

Tyuyamunite, found in Turkman, averages 1.3% U3O8, with radium,

vanadium, and copper Autunite, or uranite, is a secondary mineral

from the decomposition of pitchblende The composition is mately P2O5 2UO3 CaO  8H2O It is produced in Utah, Portugal,

Cu(UO2)2P2O8 12H2O, is a radioactive mineral of specific gravity

3.22 to 3.6 and Mohs hardness 2 to 2.5 Sengierite is a

copper-ura-nium mineral found in the Congo It occurs in small green crystals

Casolite is a yellow, earthy lead uranium silicate, 3(PbO UO3SiO2)4H2O Pilbarite is a thorium lead uranate Umohoite, found

in Utah, contains 48% uranium, with molybdenum, hydrogen, andoxygen The name of the ore is a combination of the symbols of thecontained elements Uranium is also recovered chemically from phos-phate rock The phosphate waste rock of Florida contains from 0.1 to0.4% U3O8 Most uranium ores contain less than 0.3% U3O8 Solventmethods of extraction are used

UREA Also called carbamide A colorless to white, crystalline

pow-der, NH2 CO  NH2, best known for its use in plastics and fertilizers.The chemistry of urea and the carbamates is very complex, and a verygreat variety of related products are produced Urea is produced by

combining ammonia and carbon dioxide, or from cyanamide, NH2

C N It is a normal waste product of animal protein metabolism and

is the chief nitrogen constituent of urine It was the first organicchemical ever synthesized commercially It has a specific gravity of1.323 and a melting point of 275°F (135°C) Industrial grades areavailable either as prills or as a 50% solution from Columbia NitrogenCorp An ultrapure enzyme grade is produced in small quantities byBethesda Laboratories, and material for electrophoresis by Bio-RadLaboratories

The formula for urea may be considered as O C(NH2)2, and thus as

an amide substitution in carbonic acid, O C(OH)2, an acid whichreally exists only in its compounds The urea-type plastics are called

amino resins The carbamates can also be considered as deriving

from carbamic acid, NH2COOH, an aminoformic acid that

like-wise appears only in its compounds The carbamates have the same

structural formula as the bicarbonates, so that sodium carbamate

has an NH2group substituted for each OH group of the sodium

bibonate The urethanes, used for plastics and rubber, are alkyl

car-bamates made by reacting urea with an alcohol, or by reacting

isocyanates with alcohols or carboxyl compounds They are whitepowders of composition NH2COOC2H5, melting at 122°F (50°C)

Isocyanates are esters of isocyanic acid, H N  C  O, which

does not appear independently The dibasic diisocyanate of General

Mills, Inc., is made from a 36-carbon fatty acid It reacts with pounds containing active hydrogen With modified polyamines it

forms polyurea resins, and with other diisocyanates it forms a wide range of urethanes Tosyl isocyanate, of Upjohn Co., for producing

urethane resins without a catalyst, is toluene sulphonyl isocyanate.The sulphonyl group increases the reactivity

Methyl isocyanate, CH3NCO, known as MIC, is a colorless liquid

with a specific gravity of 0.9599 It reacts with water With a flashpoint of less than 20°F (6.6°C), it is flammable and a fire risk It is astrong irritant and highly toxic One of its principal uses is as anintermediate in the production of pesticides

Urea is used with acid phosphates in fertilizers It contains about45% nitrogen and is one of the most efficient sources of nitrogen Urea

reacted with malonic esters produces malonyl urea, which is the

barbituric acid that forms the basis for the many soporific

com-pounds such as luminal, phenobarbital, and amytal The malonic esters are made from acetic acid, and malonic acid derived from the

esters is a solid of composition CH2(COOH)2 which decomposes atabout 320°F (160°C) to yield acetic acid and carbon dioxide

For plastics manufacture, substitution on the sulfur atom in

thiourea is easier than on the oxygen in urea Thiourea, NH2 CS 

NH2, also called thiocarbamide, sulfourea, and sulfocarbamide,

is a white, crystalline, water-soluble material of bitter taste, with aspecific gravity of 1.405 It is used for making plastics and chemicals

On prolonged heating below its melting point of 360°F (182°C), it

changes to ammonium thiocyanate, or ammonium sulfocyanide,

a white, crystalline, water-soluble powder of composition NH4SCN,melting at 302°F (150°C) This material is also used in making plas-tics, as a mordant in dyeing, to produce black nickel coatings, and as

a weedkiller Permafresh, of Warwick Chemical Co., used to control shrinkage and give wash-and-wear properties to fabrics, is dimethy-

lol urea, CO(NHCH2OH)2, which gives clear solutions in warmwater

Urea-formaldehyde resins are made by condensing urea or

thiourea with formaldehyde They belong to the group known as

aminoaldehyde resins made by the interaction of an amine and an

aldehyde An initial condensation product is obtained which is soluble

in water and is used in coatings and adhesives The final tion product is insoluble in water and is highly chemical-resistant.Molding is done with heat and pressure The urea resins are noted fortheir transparency and ability to take translucent colors Moldedparts with cellulose filler have a specific gravity of about 1.50, tensilestrength from 6,000 to 13,000 lb/in2 (41 to 90 MPa), elongation 15%,compressive strength to 45,000 lb/in2(310 MPa), dielectric strength to

condensa-400 V/mil (16  106 V/m), and heat distortion temperature to 280°F

(138°C) Rockwell M hardness is about 118 Urea resins are

keted under a wide variety of trade names The Uformite resins of

Rohm & Haas are water-soluble thermosetting resins for adhesives

and sizing The Urac resins, of American Cyanamid, and the Casco

resins and Cascamite, of Borden Co., are urea-formaldehyde.

Borden’s products are available as liquids, 55 to 66% solids, andspray-dried powder grades They are used as adhesives for plaster-

board and plywood and in wet-strength paper Resi-mat, from

Georgia-Pacific, is a liquid resin binder for glass-mat roofing andinsulation materials

URETHANES Also termed polyurethanes A group of plastic

materi-als based on polyether or polyester resin The chemistry involved isthe reaction of a diisocyanate with a hydroxyl-terminated polyester orpolyether to form a higher-molecular-weight prepolymer, which inturn is chain-extended by adding difunctional compounds containingactive hydrogens, such as water, glycols, diamines, or amino alcohols.The urethanes are block polymers capable of being formed by a liter-ally indeterminate number of combinations of these compounds Theurethanes have excellent tensile strength and elongation, good ozoneresistance, and good abrasion resistance Combinations of hardnessand elasticity unobtainable with other systems are possible in ure-thanes, ranging from Shore A hardness of 15 to 30 (printing rolls, pot-ting compounds) through A 60 to 90 for most industrial or mechanicalgoods applications, to Shore D 70 to 85 Urethanes are fairly resistant

to many chemicals such as aliphatic solvents, alcohols, ether, certainfuels, and oils They are attacked by hot water, polar solvents, andconcentrated acids and bases

Urethane foams are made by adding a compound that produces

carbon dioxide or by reaction of a diisocyanate with a compound taining active hydrogen Foams can be classified somewhat according

con-to modulus as flexible, semiflexible or semirigid, and rigid No sharplines of demarcation have been set on these different classes as thegradation from the flexible to the rigid is continuous Density of flexi-ble foams ranges from about 1.0 lb/ft3 (16 kg/m3) to 4 to 5 lb/ft3(64 to

80 kg/m3), depending on the end use Applications of flexible foamsrange from comfort cushioning of all types, e.g., mattresses, pillows,sofa seats, backs and arms, automobile topper pads, and rug under-lay, to clothing interliners for warmth at light weight Density of rigidurethane foams ranges from about 1.5 to 50 lb/ft3(24 to 800 kg/m3)

Confor, of E-A-R Specialty Composites, is a line of

temperature-sensitive urethane foams for cushioning and padding Surfaces incontact with body heat, for example, soften and conform to bodyshape while other regions remain stiff and supportive Unlike fast-recovery foams, recovery is slow They come in several stiffness